Fuelling the racehorse - time for a paradigm shift!

Article by Dr Katie Williams

What does it take for received wisdom to be overturned and new approaches adopted? Revelatory research findings? Social demand for change? Both could actually result in a change to the way racehorses are fed today as welfare and sustainability in equestrian sport are increasingly scrutinised and researchers find ways to feed and manage horses more sympathetically and sustainably. 

Can we feed a racehorse more sympathetically - evolutionary considerations 

The horse is a herbivore and as soon as we prevent them eating as they have evolved to do, there are repercussions for their health and well-being. The increasing frequency with which ulcers are being diagnosed may account for why the recommendations for the minimal amount of forage a horse requires has increased in recent years. Rendle et al. (2020) cite 1.5% of bodyweight on a dry matter basis which is the level most equine nutritionists would advocate for the long-term health of the horse. 

The glandular region of the horse’s stomach contains glands that secrete hydrochloric acid, pepsin, bicarbonate and mucus. The stomach secretes acid continuously; as the horse is a trickle feeder it has evolved to do so continuously and it is important to note that this process continues even when the horse isn’t eating. This is why periods of more than 6 hours without access to forage are a risk factor for ulcers. The volume of secretion has been shown to be around 1.5l of gastric juice per hour although this does vary at different times during the day. Consuming too little fibre and eating materials that are high in starch, means acidity levels increase in the stomach. This not only increases the risk of ulcers but also changes the environment in the stomach sufficiently to impact the microbes that live there. Microbial dysbiosis in the stomach is increasingly being linked to an increased risk of gastric disease, particularly in the glandular region which is now recognised as an inflammatory disease rather than an ulcerative one.   

There are other potential health issues to consider too. It has been shown in trials in mice for example, that a low fibre diet increases the permeability of the gut – a phenomenon known as leaky-gut syndrome. When fibre is fermented in the hind gut, one of the volatile fatty acids produced is butyrate and this is the energy used by the colonocytes (gut cells) themselves. Insufficient fibre and therefore butyrate, can compromise the health of the cells creating bigger gaps between them which allows contents of the gut that shouldn’t pass through, to do so. The racehorse is repeatedly exposed to new and different environments when travelling to different racecourses and encounters pathogens they might have no previous immunity to. Their reduced defensive barriers in the gut mean they are more vulnerable to these pathogens which can result in digestive upsets.  

So can more fibre be fed without compromising performance? 

Researchers at the Lab to Field research centre in Dijon, France believe so.  In work funded by the French government and published in Frontiers in Physiology, they found that Standardbred horses in training fed a third of their total ration as alfalfa with just 7% oats, performed comparably with those fed 33% oats (the remainder of the diet was hay). The horses were monitored over an 8 week period rather than just in a one-off standardised exercise test (SET). The replacement of a significant proportion of oats with alfalfa had no detrimental effects on performance or muscle tone and in fact, altered energy metabolism in such a way as to potentially improve performance and recovery the authors suggest (Martin et al., 2023). Studies back in the early 2000s (Nadeua et al, 2000; Lybbert et al, 2007) showed that alfalfa was more beneficial for horses with ulcers compared to grass forages because it helps counter the increased acidity that occurs when feeding cereals. This latest study suggests that alfalfa can actually replace a significant proportion of the cereals as an energy source too. 

The prevalence of gastric ulcers means it is an issue that needs to be addressed especially when viewed in the context of equine welfare in sport. Two recent studies have again shown how alfalfa has a key role to play in this regard too. The Lab to Field research group demonstrated that clinical success with horses with EGGD was 47.7 times more likely in horses fed alfalfa pellets as part of their ration compared to those on concentrate only rations (Julliand et al., 2023). 

In addition, a study published in 2024 showed that a combination of alfalfa, sugar beet and cereal fibre fed alongside the existing ration, aided the reduction in recurrence of gastric ulcers when fed during the healing and post-medication periods. This is key for when ulcer medication is stopped and the recognised rebound increase in acid production can occur (Menzies-Gow and Shurlock, 2024). 

A key point from these studies is that the quality of fibre matters. Alfalfa and sugar beet both contain higher proportions of digestible fibre such as pectin and hemi-cellulose, rather than indigestible fibrous elements such as lignin. This means they aren’t sitting in the gut for so long but they are being digested and utilised as an energy source. If fed in chopped forms they help to increase the amount of chewing the horse does and more chew time might actually be a relatively simple step in the right direction from a welfare perspective. The pros and cons of turning out racehorses have been widely debated but for those where it isn’t (currently) practical, it is surely a positive action to at least provide the horse with high fibre materials to eat when stabled, especially when it isn’t having a negative impact on their performance.

Dispelling Myths - Facts about Fibre

How much sugar does sugar beet contain?

The pulp fed to horses is actually really low in sugar – less than 5% assuming no molasses has been added back in. This is because the sugar has been extracted for use in the human food industry and the fibrous pulp is used for animal feed. 

Why does alfalfa contain more calcium than grass forages? 

Alfalfa has really deep roots – about 3 to 4 metres – and the calcium at this depth in the soil is more available for absorption. This means that alfalfa plants can take up more calcium than grass – chopped alfalfa contains between 30 - 50% more calcium than grass forages. Early studies suggest that omeprazole is reducing calcium absorption in the horse as is seen in humans and in Swanhall et al’s (2018) study, they recommend using bio-available calcium sources in the diet to help counteract this effect. Plant based sources of calcium such as alfalfa are much easier for the horse to absorb than inorganic sources such as limestone flour. 

Why is alfalfa so low in starch?

Like other plants alfalfa makes sugar when photosynthesising but it stores any surplus sugar as starch in its roots – the part that horses don’t eat! Grass plants tend to store sugar as fructan in leaves and the stem which is why they supply the horse with more sugar. 

What contribution can forage make to a racehorse’s requirements? 

Remember that grass-based forages contain sugar, both simple sugar (glucose, fructose etc) and as water soluble carbohydrates or storage sugars (fructan). 10kgs of hay can provide around 1kg of simple sugar and in the region of 2-2.5kgs of storage sugar. This supplies around 20% of the energy required by a 500kgs horse in intense training. Additionally, forage provides energy from the fibre it contains and so overall, including the contribution from sugar, 10kgs of hay would supply around 60-70% of the horse’s energy needs depending on the quality of the forage. 

Earlier cut forages tend to be more digestible and therefore supply more energy. These tend to be the wrapped forages in the UK and other wetter and colder European countries as there just aren’t long enough periods of dry weather to make good hay very often. Why is this significant? The way forages are conserved has changed over the years so now, a more accurate description of many forages previously defined as haylages, would be ‘wrapped hay’ as they are often very dry which has meant that little or no fermentation has occurred. This means the levels of acidity are no different to a normal hay which can be seen from the analysis results in table 1. Using lactic acid levels as a marker of acidity levels shows that most of the wrapped forages analysed in the UK are too dry for fermentation to occur and so the level of acidity is no different to hay. 

Concern about using a true haylage for horses with ulcers relates to the increased acidity from the fermentation that occurs. Clearly this doesn’t apply if the forage hasn’t fermented and so a wrapped hay may well be a really useful option for a horse with ulcers. They tend to be more palatable and softer than hay. It is important to know the level of acidity before making the decision to use a wrapped forage and having it analysed is therefore advisable. 

So if the paradigm shift happens, what will a racehorse’s diet look like in years to come? 

The basis would be a good early, cut wrapped hay. The daily bucket feed would consist of 1-2kgs of oats with 1.5kgs of alfalfa pellets, 1.5kgs of chopped alfalfa and 0.5kgs of soaked sugar beet. The chopped alfalfa  contributes to the horse’s overall forage requirement so if the dry matter of the wrapped hay is around 75%, a 500kgs horse would need a minimum of 8kgs per day to supply 6kgs of additional fibre on a dry matter basis. 

Key takeaways 

• ESGD risk factors are well established and include too little fibre and too much starch 

• Feeding at least 1.5% of bodyweight on a dry matter basis is the minimum amount of forage required for long term gastric and digestive health

• Wrapped hays that have not fermented and so are no more acidic than hay are also appropriate to use for horses with ulcers

• EGGD is still not fully understood but increasingly it is acknowledged by researchers that stress is a key contributing factor

• Studies have shown alfalfa to be beneficial as an alternative energy source compared to cereals for horses in training

References 

Julliand et al (2023) Effect of diet composition on glandular gastric disease in horses. Journal of Veterinary Internal Medicine

Lybbert et al (2007), Proceedings of Annual Convention of the AAEP, Orlando, Florida, 2007. 

Martin et al (2023) Effect of high-starch or high-fibre diets on the energy metabolism and physical performance of horses during an 8-week training period. Front. Physiol. 14:1213032. doi: 10.3389/fphys.2023.1213032

Menzies-Gow and Shurlock (2024) The effect of feeding a commercial feedstuff on equine gastric squamous disease. Journal of Equine Veterinary Science. 133. 

Muller and Uden (2007) Preference of horses for grass conserved as hay, haylage or silage. Animal Feed Science and Technology, 132, (1-2) 66-78

Nadeau et al (2000) Evaluation of diet as a cause of gastric ulcers in horses. American Journal of Veterinary Research. Jul;61(7):784-90.

Pratt et al, (2022) Assessment of agreement using the equine glandular gastric disease grading system in 84 cases. Veterinary Medicine Science, 8 (4) 1472-1477doi: 10.1002/vms3.807

Swanhall et al (2018) Mineral and Vitamin Supplementation Including Marine Derived Calcium Increases Bone Density in Thoroughbreds. Proceedings of the Australasian Equine Science Symposium

Studying the feed behaviour of horses in training - why we keep on losing the battle with ulcers?

Article by Catherine Rudenko

Is this the biggest challenge when it comes to managing digestive health for horses in training? 

Keeping a racehorse healthy inside and out can be a real challenge. The nature of training and the environment in which racehorses live presents a constant set of risks. Managing those risks and balancing them against what is needed to achieve success is a fine art. 

So where does risk come from when it comes to digestive function? Are those risks manageable within the racing environment? What can you realistically expect to achieve with changes to feed, feeding practice and the use of supplements?

One of the biggest risk factors for digestive health is the stabled environment and the pattern of feeding required to fit in around a typical working day for stable staff, coupled with the need to get out on the gallops. On top of this is then the individual’s feeding behaviour, something that can easily be overlooked when the ‘what is fed’ is the same for all horses on the yard. Individual behaviour is perhaps one of the hardest aspects to tackle, whilst replicating a natural feeding pattern is nearly impossible.

The most common digestive concern is gastric ulcers, and many feeds and supplements are now available and marketed for this condition. Yet ulcers still exist and continue to frustrate many trainers despite making dietary changes. Why is this? The answer lies in gaining a better understanding of what a ‘good’ feed pattern and diet looks like from the horses’ perspective versus what is effective for performance and realistic in a typical racing yard. 

What is a natural feeding pattern?

Free ranging horses typically show 10-15 distinct feeding bouts in a 24-hour period (1).

Time spent resting or engaged in other non-feeding activities will not normally exceed 3-4 hours per session (2). Meaning the stomach is rarely truly empty.

The majority of feeding behaviour happens during daylight hours, typically 60-70% of time available (3).

During nighttime hours the amount of time spent as feeding behaviours reduces to 40-50% of those hours (3).

The total amount of time spent grazing across multiple feeding bouts is connected to the season and daylight hours. During summer months intake is around 14 hours in total versus 12 hours in the winter (4).

The natural feeding pattern is driven by the design of the horses’ digestive anatomy and is key to good health and normal function. The further away from these patterns we move any horse the greater the risk of dysfunction. 

What is a typical feeding pattern for a horse in training? 

The time study below shows the time taken for a group of 5 horses in training to eat their bucket feed and forage allocations in a 24-hour period. All horses in this observational study were in full training and worked in the morning of the study at different time points depending on their lot. Horses were observed from 4:45am until 9:15pm.  

One of the key aspects of natural feeding behaviour is the amount of feeding periods or ‘mini-meals’ a horse consumes. For 4 out of the 5 horses from completion of their evening forage to the next meal of breakfast was a period of time in excess of 8 hours , approximately 33% of the 24-hour period. During these nighttime hours feeding behaviour normally occurs in free ranging horses and supports regulation of the digestive system. 

For wild horses the total time spent eating is 12-14 hours in a 24 hour period. They do not normally have periods exceeding 12 hours in every 24 without some form of intake. For 4 out of the 5 horses there were distinct periods where all feed and forage had been consumed. The amount of time without any feed or forage available for the horses ranged from as little as 3 hours and 40 minutes up to 15 hours 30 mins in a 24-hour period.

Natural feeding patterns rarely see more than a 3-4 hour gap between each ‘mini-meal’ and at these points where gaps exist, it is important to remember that food has been available for 24 hours without restriction leading up to these chosen breaks in forage intake. The break in intake is short and during this time the stomach is unlikely to be truly empty. For horses in training it is easy to have periods in excess of 3 hours without any intake of feed or forage. 

Although the period from finishing breakfast to morning forage being given was for some horses less than 3 hours, the stomach when receiving that breakfast was in a fasting state. Ordinarily in the natural environment the stomach is rarely truly empty as it can take anywhere from 2-6 hours for the stomach to empty depending on what and how much has been consumed (5). When giving a bucket feed to a horse in a fasting state the rate of transit of that feed through the stomach will be relatively short, and depending on which lot the horse is pulled out for, can result in the horse being worked on an empty or near empty stomach. 

Why does this matter? 

One of the common causes of squamous ulceration is ‘acid splashback’ which relates to strenuous exercise and the movement of acidic content from the lower glandular region of the stomach to the unprotected squamous area (6). When the stomach contains feed or forage it is more difficult for the acidic content to be forced upwards to the squamous area. This is why it is recommended to include chaff in the breakfast feed or provide a small amount of forage as these fibrous sources are slower to pass through the stomach and can help reduce the level of acidity seen in the proximal portion of the stomach. The key point here is reduction not elimination. The practice will not prevent ulceration occurring, but it will reduce exposure.

The table below shows the difference between horses that were fasted for only 2 hours before exercise and those fasted for 18 hours. 

One of the challenges in racing is the differing amount of time between the breakfast feed and being saddled up for work. On top of this some horses will naturally consume their allocated feed faster. Even within the small number of horses observed in the study in Figure 1 there was notable variation in the time taken to eat the same amount of bucket feed given. Some of this variation comes from giving all horses the same breakfast by weight, which represents a different meal size against their bodyweight. Variation also exists as racehorses are individuals and appetite is flexible and influenced by other factors such as level of fitness and stress.  

Figure 3 shows the amount of dry matter provided in the breakfast feed to each horse and considers it against the bodyweight of the individual horse. The breakfast given was 2.2kg of a cubed racing feed alongside 0.6kg of an alfalfa based chaff. 

Can feed intake be slowed down?

In terms of feed format, pelleted feeds are consumed faster than mueslis or ‘sweet feeds’ (7). The addition of chaff mixed with the feed can slow intake, but for it to be effective there must be a reasonable amount given compared to the amount of pelleted or textured feed. As a rough guide, providing an additional 30% of the hard feed weight as a chaff will make a notable difference to the rate of intake. 

Whilst the aim is to slow intake it is important to keep in mind that feeding hard feeds too close to strenuous exercise is not recommended. Ideally feed is withheld for 2 hours before exercise. Forages, eg hay, haylage and alfalfa chaff, do not need to be removed but intake should be restricted to a small amount, typically 1kg. Providing a small amount of forage in this format helps maintain saliva production, which assists with regulation of acidity, and provides some fill for the stomach. 

Does forage intake matter?

Risk factors for gastric ulceration and colic when it comes to forage are similar. Diets low in forage and high in concentrates increase risk, along with intermittent feeding patterns and/or periods of fasting. 

In addition to what is given and the pattern that fits practically at a yard, is the fact that horses, like many other species, do not have a fixed rate of intake when a meal of any sort is presented. The majority will have a higher consumption rate at the start of feeding than at the end. With the observed horses hourly weigh backs of forage were carried out for a period of 6 hours to determine rate of consumption. During this time no bucket feed was present.  Figure 4 shows the individual intakes.

In the case of horses in training this is another problem to consider when it comes to evening feeds. Whilst the amount of forage given may be reasonable and in line with expected appetite, the feeding behaviour of the horse means there is not a consistent or regular intake of forage observed until the following morning feed.  True feeding of ad-lib forage, above what a horse needs or could eat in a 24-hour period, is rarely given and often impractical. The reality is that most horses in training will have a prolonged period of zero feed or forage intake during nighttime hours, which is the opposite of natural feeding behaviour. 

This is a practical challenge which for many yards is not easily overcome. Ideally forage should be fed at more regular intervals, rather than twice daily, to more closely replicate the 10-15 feeding bouts observed in wild horses. 

What can be done to improve feed patterns?

Simply put, the longer a horse spends eating the better. 

An enthusiastic eater that is ‘keen at the pot’ might be taken as a sign of good health, but a speedy intake that leads to a feeding pattern with longer periods between any sort of meal isn’t necessarily a good thing. A horse that appears a little slow with their forage but still consumes a good amount over a daily basis is not a bad thing as the pattern of eating is closer to multiple mini meals. 

• Using a good amount of chaff in every feed will prolong feed intake and requires additional chewing which helps increase salivation. 

• In the case of morning feeds ideally a little hay or haylage could be given, particularly for later lots to ensure the presence of some fibre in the stomach when working. Such a presence will not completely stop acidity in the delicate squamous area of the stomach, but it will reduce it. 

• Providing the evening forage as late as is possible to reduce the amount of time between evening forage being consumed and breakfast given. 

• Taking note of ‘speedy eaters’ and considering if hay nets or hay feeders would be appropriate to prolong the time taken to consume their evening allocation. Hay nets in different locations in the stable, for example one at the front and one at the back, can also influence how quickly all the forage is consumed. 

• Consider the type of forage given. Hay can be easier to provide on more of a free choice basis as horses will consume less hay than haylage on a dry matter basis in a set period of time (1).

What is a realistic expectation for managing digestive health?

The need for high energy intakes to fuel performance means reliance on hard feeds and a limited amount of forage. The horse does not have an unlimited appetite and even when provided with additional forage will not necessarily consume enough or consume it in a regular fashion. Replicating a natural feed pattern for horses in training is close to impossible and inevitably results in digestive disorders, but making changes and trying to reduce that risk is worth doing. The differences made may be small, but winning margins can be just as small.

The purpose of feeding low starch diets to horses in training is to reduce the specific element of risk that comes from high starch feeding. In doing so that element of risk is managed and the diet is one step closer to a more natural fibre-based diet. But it is one area of risk alone and mitigating this risk does nothing to control the risk of ulcers or colic from intermittent feeding, the impact of withholding water,  the effect of travel and the physical effects on the stomach from strenuous exercise in the case of ulcers.

Using supplements that support healing of tissues, the function of mucus barriers or buffer acidity in the stomach are all part of trying to manage gastric ulcers, a disorder that is created through the training environment and the intensity of work required to achieve a race fit state. Such supplements are not designed to treat or prevent ulcers, they are not medicines and should not claim to do so, but they play an important part in trying to maintain a healthy digestive system.

Equally using supplements that support hindgut function through promoting the growth of beneficial bacteria, stabilising the pH of the hindgut or ‘mopping up’ pathogenic bacteria are all part of trying to maintain a healthy hindgut, which has many benefits, and reduces the risk of disorder within this section of the digestive anatomy. 

The most important thing when considering gastric ulcers and other digestive disorders is to be realistic about what you can achieve within your environment, and to be realistic about what difference feeds and supplements alone can make. Any steps that can be taken to reduce risk are worth implementing as the aim is to keep the digestive system as healthy as possible so that the food you provide is converted to the nutrients needed to maximise performance and maintain general good health.

References

1. Ellis,A.D.,2010. Biological basis of behaviour in relation to nutrition and feed intake in horses. In A.D. Ellis, A.C.Longland, M.Coenen & N.Miraglia, ed. The impact of nutrition on the health and welfare of horses. The Netherlands: Wageningen Academic Publishers, 53-74

2. Ralston,1984; Vulink,2001, cited in Ellis,A.D.,2010. Biological basis of behaviour in relation to nutrition and feed intake in horses. In A.D. Ellis, A.C.Longland, M.Coenen & N.Miraglia, ed. The impact of nutrition on the health and welfare of horses. The Netherlands: Wageningen Academic Publishers, 58.

3. Vulnik,2001; Boyd 1988; Berger et al.,1999; Edouard et al.,2009 cited in Ellis,A.D.,2010. Biological basis of behaviour in relation to nutrition and feed intake in horses. In A.D. Ellis, A.C.Longland, M.Coenen & N.Miraglia, ed. The impact of nutrition on the health and welfare of horses. The Netherlands: Wageningen Academic Publishers, 58.

4. Vulnik,2001 cited in ELLIS,A.D.,2010. Biological basis of behaviour in relation to nutrition and feed intake in horses. In A.D. Ellis, A.C.Longland, M.Coenen & N.Miraglia, ed. The impact of nutrition on the health and welfare of horses. The Netherlands: Wageningen Academic Publishers, 59.

5. Frape, D. (2010) Equine Nutrition and Feeding. 4th Edition. United Kingdom: Wiley-Blackwell

6. Lorenzo-Figueras,M. Merrit,AM. Effects of exercise on gastric volume and pH in the proximal portion of the stomach of horses. Am J Vet Res. 2002;63(11):1481-1487

7. Hintz et al 1985 cited in Geor,J. Harris,P. Coenen,M. (2013) Equine Applied and Clinincal Nutrition. China: Elsevier

Trust your gut - the importance of feeding the gut microbiome for health, performance & longevity

Article by Dr. Richard McCormick, M.V.B., Dip. Eq.Sc., M.R.C.V.S. 

The science of equine nutrition is really quite simple – The horse is a flight animal and in the wild, needs to be able to escape from predators using a short burst of energy. Nutrition and subsequent ‘energy’ for survival is all provided by grass which has the required balance of vitamins, minerals, immune supportive nutrients and  fibre to maintain a healthy gut microbiota and keep the horse in adequate health for reproduction. Proper functioning of the gastro-intestinal tract (GIT)  in horses is dependent on a broad range of micro-organisms and more than half of the energy requirement for their survival comes from the microbial fermentation occurring in their enlarged caecum and colon (Chaucheyras-Durand et al 2022). The bacterial populations resident in the various compartments of the horses intestinal tract vary greatly (Costa et al 2015) and there is more DNA in the bacteria located in the gastro-intestinal tract  than there is in the entire body. Because of this, having a healthy gut flora is critical to having a healthy immune system.

In modern times, our demands of horses for performance for our pleasure rather than their survival has led to their need for increased energy that cannot be provided from grass alone. Because of this, the intricacies of diet (in particular the consumption of starch, fibre and fat) has come under scrutiny. Equine feed manufacturers have looked for additional sources of starch, a carbohydrate and a natural component of grass that is ‘essential  to provide energy, fibre and a sense of fullness’ (Seitz 2022). Today, most horses and rapidly growing foals are commonly fed diets with >50% of total ration by weight in the form of grain ‘concentrates’ and carbohydrates from oats, maize, soya, barley and wheat. These grain based feeds contain high concentrations of soluble, easily fermentable starches but can be deficient in certain minerals and vitamins so getting an optimally balanced feed ‘right’ is difficult.

Too much of a good thing  

With advances in scientific knowledge, we now know that when a horse is exposed to surplus starch, the hydrogen ion concentration of their gut increases promoting  the production and absorption of lactic acid, acetate and propionate through the activity of fermentation (Ralston 1994). The process is quick, with lactic acid entering the bloodstream within 3 hours of feeding and calcium subsequently being excreted in the urine.  In order to combat this nutrient loss, the horses’ hormone system triggers the release of parathyroid hormone into the bloodstream, activating the release of stored calcium (to maintain optimal blood levels) but unfortunately causing  bone demineralisation. Clinically, the horse experiences health consequences of varying degrees including digestive diseases (eg: gastric ulcers, diarrhoea, colic or colitis), muscle dysfunction (eg: rhabdomyolysis (known as ‘tying up’), defective bone mineralization (expressed as increased incidence of stress fractures and developmental orthopaedic diseases), systemic diseases (such as laminitis, equine metabolic syndrome and obesity (Chaucheyras-Durand et al 2022) as well as potential causes of fatigue.

The ideal equine diet 

There is little equine focused research available on the benefits of individual nutrients (due to limited numbers in trials and their subsequent evaluation) of grain ‘concentrates’. But we do know that ingredient availability and quality is regularly influenced by market pressures. 

The table (fig 1) below outlines the sugar, starch and fibre components of the various ingredients commonly found in horse feeds. The optimal grain for equine nutrition with its efficient energy source through lower starch content (relative to other grains) and its high level of soluble fibre (relative to other grains) are oats.

Oats are highly digestible and do not require heat treatment or processing prior to feeding (unlike all other grains). They are the only grain that is easily digested raw and the least likely to cause insulin spikes and blood sugar fluctuations. Unfortunately, oats are not a ‘complete’ nutrient source as they are high in phosphorous and low in calcium. For adequate bone and muscle development as well as proper blood formation, oats must be balanced with additional vitamins and minerals.

The healing power of omegas and short chain fatty acids 

While grass provides optimal equine nutrition in its own right, the ‘curing process’ when making hay depletes the valuable omegas 3 and 6 intrinsic in grass. These ‘healing’ nutrients naturally protect the lining of the gastro-intestinal tract by increasing mucous production and alleviating ‘auto digestion’ (via hydrochloric acid). For horses, bacterial fermentation in the hind gut also results in the production of Short Chain Fatty Acids (SCFAs), namely acetic, proprionic and butyric acids. These SCFAs ‘cross talk’ with the gut immune system providing local immunity in the gut as well as protection of the respiratory system, the brain and other tissues against disease. In human medicine, it has been repeatedly established that a dysfunctional gut microbiome is associated with respiratory problems. This is evidenced by the fact that when gut disorders such as Irritable Bowel Syndrome  (IBD) or Coeliac disease exist in humans, they are commonly associated with a higher incidence of respiratory infections and related asthmatic like conditions. Barragry (2024) explores the relationship (Fig 2) between gut microbiome and the immune system's ability to support health and combat disease in cattle. A scenario mirrored in the equine.

The stabled horse should be provided with SCFAs daily to support proper functioning gut microbiome. This critical dietary consideration should ideally be provided in the form of flaxseed which has the highest ratio of omegas 3 and 6 (in the ideal ratio 4:1) in the plant world and is most suitable for the equine herbivore.

The health benefits of flaxseed for both humans and equines has been recognised as early as 3,000 BC. Flaxseed was used for various medicinal purposes such as the treatment of gastric disorders, as a soothing balm for inflammation and as a laxative (Judd, 1995). Horsemen (who relied heavily on their equines) and trainers (who sought optimal performance from their charges through natural means) also used flaxseed as a way to supplement the diet with omega-3’s and fibre to produce high quality proteins. Now, thirteen centuries later, we have research to substantiate the knowledge of our ancestors. The renowned German researcher of ‘fats’ and pioneer in human nutrition, Dr. Joanna Budwig, as early as the 1950’s reported that “the absence of highly unsaturated fatty acids causes many vital functions to weaken". Dr. Budwig’s life’s work focused on the dietary ‘imbalance’ between omega-3 and omega-6 fatty acids in humans has been a cornerstone to the exploration of the role of inflammation and the development of many diseases of the coronary, respiratory, metabolic and immune system.

The small seed of the flax plant is also an excellent source of high-quality protein (exceeding that of soybeans and fish oils) and potassium (a mineral that’s important for cell and muscle function). But, the true power of flaxseed lies in three key components: 

Omega-3 essential fatty acids – Also known as "good" fats, omegas enhance the oxygen usage of cells and in combination with alpha-linolenic acid (ALA) are anti-inflammatory in their effect within the body.

Lignans – Flaxseed contains 750 - 800 times more lignans than other plant foods (McCann 2007, Yan 2014). Lignans are a group of compounds with antioxidant properties which also contain plant oestrogen. Lignans are linked to a reduced risk of developing osteoporosis, heart disease and cancer.

Fibre - Flaxseed contains both the soluble and insoluble types of fibre essential for maintaining ‘gut’ health.

In equines, adding flaxseed to the diet has the immediate benefits of a shiny, healthy coat and fewer skin allergies. Consistent use of flaxseed has multiple long term benefits including strong hoof quality, improved joint health, reduced muscle soreness, faster healing of ulcers (Sonali et al 2008) and significantly impacts inflammation associated with chronic skin conditions (commonly known as ‘sweet itch’). In breeding stock, increased Omega-3 levels in mares’ milk leads to boosted immunity in foals with higher stallion fertility and improved conception rates in broodmares documented (Holmes, 2015).

How diet can influence performance 

It is easy to think that ‘providing more is better’ when it comes to using nutrition to support performance. But having excess levels of essential vitamins and minerals being processed by the horses’ sensitive gut has a direct impact on their behaviour and willingness to perform. Today, we have greater ‘choice’ at the feed store with a broad range of commercial feeding offerings available including mixes, mashes and supplements but the discerning horse owner can be forgiven for being overwhelmed by the range of diet options for every ailment and stage of life.

In modern times, despite advances in nutrition offerings, we have seen a falloff in performance (Fig 3). During the late 1960s, the U.S. Jockey Club stats noted that racehorses averaged 12 starts per year – a far cry from today's horses racing in the U.S. where the average of 3 ‘starts’ was highlighted by leading US Trainers in 2020 (www.ownerview.com). Unfortunately, this is not just a U.S. based problem, but a phenomenon noted worldwide. 

The first equine pelleted feed was formulated in the US by the Cistercian  monks in Gethsemani, Kentucky in 1957. Prior to this, all horses were fed ‘straights’ (primarily oats as their energy source and flaxseed as their protein source). My own understanding of the link between modern feeding practices and compromised performance since the 1960s has been curated off an understanding of “what was different” then, as well as a career of observations, clinical practice and scientific review. Fact is, the equine diet of the 1960s was lower in starch and high in fibre. It consisted of oats, minerals, and flaxseed as the “norm”. Hay was the preferred forage (Fig 4).

Today, soya (with one fifth of the omega 3 content of flaxseed) has practically replaced flaxseed as the protein source in equine nutrition. This small change has seen a significant drop in omega-3 and 6 (needed for prostaglandins) in the diet with consequential gastro-intestinal and joint issues. Other dietary changes include those recommended by the National Research Council (NRC) in 1978, who suggested doubling the recommended calcium levels for horses with a subsequent increase in levels of Osteochondrosis (OCD) and Osteopetrosis in the equine population (Krook and Maylin, 1989). Additional moisture in the diet too has led to excess mould formation in convenience feeds and with severe exposure causes liver damage (Buckley et al 2007). Stabled racehorses today mostly lack the nutritional protection afforded a previous generation of horses. The impact has been noted clinically in the widespread increase in equine gastric issues and as stated by J.E. Anthony “Racing fans are missing about half of what they once enjoyed in racing.”

The role of the gut bacteria in the prevention of disease

The gut microbiome begins populating and diversifying from the moment of birth. Though ‘sterile’ in utero, gut derived DNA immediately drives immune health with exposure to nutrition. Recent research suggests that the gut microbiome can be stimulated by using proven probiotics with a track record in enhancing gut health (Barragry 2024). But it is the protective power of SCFAs to allow ‘cross talk’ between the lungs and the gut microbiome that is critical to supporting horses through their lifespan. 

Nutrition using grain ‘concentrates’ is currently at approximately  99% saturation in today’s equine population so a return to feeding ‘straights’ is a swim against the tide of modernity. But, knowing the influence of nutrition on health, performance and longevity it falls on horse owners to be mindful of the consequential  impacts  such convenience feeds have on the gut microbiome and immune system. Random supplementation and high starch feeds are leading to dietary health issues such as gastric ulcers, hyperinsulinemia and  hyperlipaemia (obesity) as well as increased risk of laminitis . So trust your gut and keep it simple – a diet of oats, flaxseed, a multi-vitamin balancer and ad lib hay will not only meet your horses’ energy needs but will keep them happy and healthy too.

REFERENCES

Barragry. TB (2024) WEB https://www.veterinaryirelandjournal.com/focus/254-alternatives-to-antibiotics-probiotics-the-gut-microbiome-and-immunity

Buckley T, Creighton A, Fogarty (2007)  U. Analysis of Canadian and Irish forage, oats and commercially available equine concentrate feed for pathogenic fungi and mycotoxins. Ir Vet J. 2007 Apr 1;60(4):231-6. doi: 10.1186/2046-0481-60-4-231. PMID: 21851693; PMCID: PMC3113828.

Budwig, Dr. J (1903-2008) WEB https://www.budwig-stiftung.de/en/dr-johanna-budwig/her-research.html

Chaucheyras-Durand F, Sacy A, Karges K, Apper E (2022). Gastro-Intestinal Microbiota in Equines and Its Role in Health and Disease: The Black Box Opens. Microorganisms. 2022 Dec 19;10(12):2517. doi: 10.3390/microorganisms10122517. PMID: 36557769; PMCID: PMC9783266. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9783266/

Holmes, R (2015) Feeding for stallion fertility. WEB 

https://www.theirishfield.ie/feeding-for-stallion-fertility-172113/

Judd A (1995) Flax - Some historical considerations. Flaxseed and Human Nutrition, S C Cunnane, L U Thompson. AOCS Press, Champaign, IL 1995; 1–10 [Google Scholar]

Martinac, P (2018) What are the benefits of flaxseed  lignans?  WEB https://healthyeating.sfgate.com/benefits-flaxseed-lignans-8277.html

National Research Council. 1989. Nutrient Requirements of Horses. Washington D.C.: National Academy Press.

Ralston, S VMD, PhD, ACVN (1994) The effect of diet on acid-base status and mineral excretion in horses in the Journal of Equine Practice. Vol 16 No. 7. Dept of Animal Science, Rutgers University, New Brunswick, NJ 08903

Seitz, A  (2022) What to know about starch_Medically reviewed by Seitz, A - MS, RD, LDN, Nutrition — WEB https://www.medicalnewstoday.com/articles/what-is-starch#benefits

Sonali Joshi, Sagar Mandawgade, Vinam Mehta and Sadhana Sathaye (2008) Antiulcer Effect of Mammalian Lignan Precursors from Flaxseed, Pharmaceutical Biology, 46:5, 329-332, DOI: 10.1080/13880200801887732

Steps to take in order to prevent respiratory disease after a poor harvest

Article by Alan Creighton (Head of environment and nutrition at the Irish Equine Centre)

I don’t want to sound alarmist because I am generally a very positive person, but I have no doubt that there will be an increase in racehorse respiratory issues this winter and next spring due to a combination of poor hay and straw harvests in conjunction with a very damp autumn. 

Through our everyday testing at the Irish Equine Centre we have already seen higher than average fungal contaminated hay, haylage and straw submitted for testing this autumn. Our routine monitoring of racing yard environments in Ireland, the UK and France are also showing increases in fungal contamination in air samples and surface swabs taken throughout the yards. The damp weather conditions from the second week of June right through the summer in western Europe resulted in fields of grass and cereal crops which were showing major signs of fungal contamination while still standing in the field. 

It didn’t get much better when the dry spells came in early September. Land was already saturated which meant the crops once mowed were extremely difficult to dry which has resulted in discoloured, dusty, high moisture straw, many hay stacks which heated and oats with high moisture content. Even haylage, which is the normal go to method of preserving forage when conditions are poor has shown much higher levels of contamination thus far. Damp weather in this period also meant that stables themselves were often damp which encouraged fungal growth on the internal surfaces.

Racehorses are athletes that need a fully functioning respiratory system to maximise performance. IAD, COPD, RAO (all forms of equine asthma) and EIPH (bleeding) are respiratory conditions which are major causes of poor performance in racehorses.  Fungi and mycotoxins are now recognised as a major cause of these conditions and in particular the pathogenic fungus Aspergillus being the main culprit. 

Fungi that penetrate the airways can cause unwanted inflammation and can be infective, toxic, allergenic or all 3 combined. The further the distance a racehorse is asked to race, the more detrimental this inflammation will be to performance. The main sources of this fungus are in hay, haylage, straw and oats. 

This fungus is a storage fungus and so it propagates in stored foodstuffs overtime where the moisture level is above 14%. When the fungus contaminates a foodstuff or bedding the horse has no choice but to breathe in the harmful spores in their stable environment. The fungus also causes a level of immunosuppression which can often be the precursor to secondary bacterial and viral disease. 

The cost of bedding for racehorses has been steadily rising over the last number of years. Wood shavings have become very expensive to buy but are now also very expensive to dispose of. Straw is still more cost effective to buy and much more cost effective to dispose of. 

I will often get asked the question “what is the best bedding for horses?” - my answer is consistently “good straw”. When I get asked the question “what is the worst bedding for horses?” my answer is consistently “bad straw”.  The cost saving in purchasing and disposing of straw has made it attractive to trainers in a time when all other costs are rising. Finding good straw this year will be very difficult. 

In many countries in Europe, we have a government policy called SIM, the Straw Incorporation Measure which is a payment for chopping straw and incorporating it into the soil. SIM has been designed to encourage tillage farmers to increase soil organic carbon levels by chopping and incorporating straw from cereal crops and oilseed rape. 

Unfortunately, an unintended consequence of that policy is the reduction in availability of straw for bedding purposes. This is particularly problematic this year because now we have a shortage of straw and the straw which is available for bedding has much higher levels of harmful moulds due to the poor harvest conditions. 

When feeding haylage, the spoilage process can begin quickly if the bale is exposed to air, this may be due to damage of the wrapping or not using the bale quick enough once opened. Fungal spores will develop and this should be carefully assessed before feeding. This is a major problem we encounter on a regular basis. Often trainers are feeding big bales of haylage to a small number of horses which means the bales are exposed to air for a prolonged period of time. 

Pathogenic fungi will develop very quickly and often lead to both respiratory and gastric problems. For that reason, the IEC will recommend to use haylage once opened inside of 4 days in the winter and 3 days in the summer. This recommendation will often determine the choice between hay and haylage as you would therefore need to be feeding a larger number of horses to feed large bale haylage. 

Hay production requires 7-10 days of continuous good weather unless you are barn drying. In Ireland and the UK we got a two week spell of suitable weather in the last week of May until the end of the first week of June. Many meadows were not ready, and the ones that needed patience from the farmer not to bale too early as hay at that time of the year is very difficult to dry properly due to the lushness of the grass. 

Having said all that, the best hay of this season was made in that period. That was the only spell until a two week spell in September. Historically, the best hay in western Europe is made from the middle of June to the end of July. That was not possible this season. The hay made in that early spell is very good in terms of quality but very poor in terms of volume. The hay made in the second spell in September was very high in volume but very poor in terms of quality. The nutrition levels of this September hay is also poor and the fungal levels are very high.

At the Irish Equine centre we analyse thousands of samples of hay, haylage, chaffs, straw and oats every year for both hygiene (mould and bacteria levels) and nutritional content. The reality is that in a normal year with good spells of weather we still get both hay and haylage with extremely good nutritional and hygiene values and we get hay and haylage with very poor nutritional and hygiene values. 

This year the percentage of poor is outweighing the percentage of good. Normally we would advise that trainers should produce or purchase enough of the same batch of quality forage for the whole season. That may not be possible this year. It is our experience from testing forage that getting haylage with consistent nutritional values can be very difficult even in a good year. This is mainly due to the variants in moisture content which will certainly be the case this season. Hay which is well made and stored well does tend to be much more consistent and therefore better for overall horse health. 

Both hay and haylage are prone to fungal contamination in different ways. With haylage the fungal contamination occurs as a result of inadequate fermentation or when air pockets or punctures occur in the plastic. 

Fungal problems in hay occur because of high moisture levels during the baling process and because of inadequate storage during winter months. We have shown in the past that those fungal problems are compounded and elevated since farmers have moved away from the traditional small bale and moved to large round and rectangular bales. Farmers who traditionally barn dry small square bales, who ensure that hay is dried below 14% moisture and then covered (a layer of clean bales of straw) in storage remains the most hygienic hay for racehorses.

During storage the moisture level on the outside of uncovered bales significantly increases over damp winter months, leading to a significant increase in fungal growth. Round bales suffer the worst during storage. Hay in large bales needs to have a very low moisture level when baling, which just wasn’t possible in most cases this year when field drying. 

When this type of bale has a high moisture level in the centre of the bale it results in significant increases of pathogenic fungi contamination during storage. We have shown through studies that keeping the moisture level of hay below 14% moisture will significantly reduce Aspergillus contamination. It was very difficult to achieve this moisture reduction this summer and often farmers had no choice but to treat the hay with buffered propionic acid which is an effective preservation method which reduces fungal growth during the early stages of storage but its effect diminishes over time.

Good quality tested hay is still the most beneficial to horses when all factors are taken into account. Once purchased hay should be stored properly by the supplier to ensure that it remains consistent. The hay supplier should ideally guarantee the trainer a supply of hay which is consistent for the whole season rather than swapping and changing batches constantly. 

All hay should be covered from the end of September once the moisture content has stabilised to protect it from damp air during winter months. Trainers with inadequate storage may have no choice than to feed haylage. If this is the case, buy the right size of bales for the amount of horses you are feeding. 

Steaming of hay in the correct manner can be a very useful process to reduce the fungal load in contaminated hay. Some producers of hay harvested very early this year to take advantage of that good weather spell. First crop hay when harvested early can be difficult to save and can have a very high protein content. That high protein is good if you test it to quantify the actual protein content and you then balance your feeds accordingly.

If high protein hay or haylage is used and feeds are not adjusted accordingly it can overload the digestive system with nitrogen. Excess of protein will also lead to an over production of urea, leading to an excess of ammonia emissions in the stable which can also cause respiratory irritation.

So, what is the advice from the IEC? Trainers will need to test their hay and haylage at multiple stages during their season as the dangerous fungi will develop over time. The volume of suitable forage and bedding will be low, so trainers should act quickly to secure the best that’s available. 

The nutrition department at the IEC provides full nutritional and hygiene testing for hay, haylage, straw and oats. It is vital that you test forage pre-purchase when trying to buy a season's supply. Hay, haylage or bedding contaminated with pathogenic fungi will cause respiratory disease which will affect racehorse performance. 

For that reason, the cost of testing forage is a small price to pay rather than losing significant portions of the season due to poor performance as a result of respiratory disease. How you store and feed hay, haylage, and oats will have a huge impact on the level of exposure your animals will have to harmful moulds. Stable hygiene and ventilation will be even more critically important when the risk of contaminated inputs is so high.

To conclude, trainers should always acquire the best possible forage and bedding available and test it prior to purchase. You can and should inspect and test any batch of hay or bedding properly prior to delivery. You can take a representative sample for the testing lab which can then be the deciding factor for your purchase. When taking a sample, take a fistful from 6-8 different bales in the stack to ensure you get a representative sample. 

We monitor the stable environments of over 200 racing yards in Ireland, the UK, France and in the Middle East. That monitoring includes hygiene sampling of feed, forage, bedding, water, stable surfaces, walker surfaces and air quality in barns. The benefits of that monitoring for the trainer is that you highlight issues which can cause respiratory disease, proactively prevent disease problems and finally have a mechanism which quantifies the effectiveness of stable disinfection routines. 

The most consistent trainers in terms of performance have good hygiene practices. If anybody would like to discuss the above issues or need help with assessing the quality of forage and bedding in use, please contact myself or any of my team at nutrition@irishequinecentre.ie and we would be glad to help.

The role of the lymphatic system in energy metabolism

Article by Peter Bollen, head nutritionist Cavalor

In recent years, focus has turned towards the emerging science of the lymphatic system. It is as important as the circulatory system (which includes the heart and the blood vessels), and is fundamental to the functioning of the body and central to the immune system, energy metabolism, detoxification and energy availability in the horse’s body.

A horse with a well-functioning lymphatic system can metabolise energy and clear metabolic waste more efficiently, leading to enhanced performance and faster recovery. 

So how can we tap into the benefits of an effective lymphatic system? Well, the first step is in understanding what it is. We might know that nutrients and oxygen are carried in the bloodstream towards our tissues, but what about how they are actually delivered to the cells?

This is where the lymphatic system comes in. Broadly speaking, it runs in parallel to the circulatory system and creates the point of delivery to the cells and tissues. The circulatory system carries the blood via arteries and vessels, which get smaller as they reach the muscle tissue as capillaries - where the wall is only one cell thick.  

This enables smaller molecules such as nutrients and oxygen to be pushed out of the capillaries and into the fluid around the cells - or lymph - while retaining larger cells like erythrocytes (red blood cells). 

The lymphatic system is an extensive network of vessels and nodes that transports lymphatic fluid around the body and it has two main functions:

1. Energy metabolism - transporting nutrients and oxygen to the cells

All the cells and tissues of a horse’s body are surrounded by a watery gel-like substance called interstitial fluid. This provides a medium for dissolved oxygen and nutrients to travel across to the cells. Lymph capillaries, carrying these substances, run through the interstitial fluid. The walls of these capillaries are also only one cell thick and have overlapping junctions, which make them highly permeable and allow easy transfer of materials.

In practical terms, this means the horse’s muscles and tissues get all the energy they require to carry out all their metabolic processes. As well as being responsible for giving cells the oxygen and nutrients they need, the interstitial fluid transports salts, hormones, neurotransmitters, coenzymes, amino acids, sugars and fatty acids around the body via the lymphatic system.

“A horse with a well-functioning lymphatic system can benefit from increased energy and enhanced performance, but without feeling too fresh or fizzy”

2. Detoxification: processing waste products

During the season, horses are placed under physiological demands and their body has a lot to process. In hard exercise and in races, their body will produce a lot of waste products. Their thin-walled lymph vessels also allow interstitial fluid into them to remove the waste products of cell metabolism (such as cell debris, bacteria, dead blood cells, pathogens, toxins, lactic acid and protein molecules) from each cell. This process is just as important as carrying necessary materials to the tissues to provide energy. 

These metabolic waste products are carried in the lymph away from the cells for detoxification. This is the term used for the continuous processes in the horse’s body to remove those waste products or metabolites that are naturally produced.

Detoxification takes place mainly in the liver, kidneys and intestines, so it is really important to ensure that those organs in the horse are healthy and functioning well. By supporting the liver and kidneys, you can help this breakdown process and allow the horse to better metabolise compounds that would otherwise be toxic if they remained in the body.

Gut health is also very important to the lymphatic system and detoxification, given that more than half of the lymphatic vessels of the horse are located within the gastrointestinal tract. 

Peristalsis (the natural contraction and relaxation of the gut wall) drives the return of lymph to the rest of the body. Movement in the gut is stimulated by food consumption (mainly long fibres) and is crucial to lymphatic system function as there is very limited muscular contraction in the horse’s lymphatic vessels themselves. This means it relies on passive forces from movement of other systems in the horse’s body as opposed to active muscle contractions.

Ensuring sufficient feed for a horse around the clock is crucial, not only for maintaining gut health, but to maintain a healthy immune system and detoxification process as well.

Lymphatic system and immune function

In addition to lymph and lymph vessels, the horse has around 8000 lymph nodes. These bundles of lymphoid tissue and proteins act as a filter for foreign substances that travel through the lymphatic fluid and contain lymphocytes (white blood cells) that help the body fight infection and disease. This means that the lymphatic system is also key to the functioning of the immune system.

As the lymph tissue approaches each lymph node, it slows down and collects in that area. Horses have so many lymph nodes that they are extremely susceptible to lymph node blockage. Lymph nodes can actually be felt or sometimes seen at various points around the horse’s body, particularly around the head and neck or when they are swollen.

Keep on moving

Movement is so important for horses, precisely because of the fact that there are no direct muscular contractions within the walls of the lymph vessels to promote the flow of lymph. The functioning of their lymphatic system relies on the force of movement of other structures in the body, such as the movement of the skin to apply pressure to the underlying tissues and stimulate the transport of lymph through the vessels.

In the modern day, racehorses can be stabled for longer periods of time. It is very common to see leg swelling, which has a very simple explanation in terms of the immune system. This principle of continuous movement being necessary applies especially to the legs, where this elastic movement of the skin is assisted by a pump mechanism in the hoof and fetlock joint. It is thought that this is the case due to there being no muscles in the lower limbs of the horse to aid the movement of lymph from this area.

Horses therefore need to move extensively and perhaps almost constantly (up to 16 hours per day) to keep the lymph circulating around the body, and standing still for too long significantly impairs the functioning of the lymphatic system.

Practical tips for a healthy lymphatic system

1. Turn horses out as much as possible  

Horses that are standing still for long periods of time are at risk of an impaired lymphatic system, which can impact the immune system, recovery time and ultimately performance. Turnout makes a happier horse and a healthier horse.

2. Cool down for at least 15 minutes after exercise

The period of time immediately after training is important for removal of metabolic waste products and keeping a horse moving after a hard training session stimulates the lymphatic system to continue to remove waste products from cells, which includes the removal of lactic acid. By cooling down properly after every session, you can significantly improve recovery times.

3. Consider feeding supplements that can directly benefit the lymphatic system

Functional herbal ingredients in innovative supplements can support lymphatic system function. Cleavers (Galium aparine) is known to bring benefits to the lymphatic system. Couch grass (Elymus repens), Nettle (Urtica dioica), and Dandelion (Taraxacum officinale) are all known to have purifying effects which can support metabolism and detoxification.

Even Lionel Messi, Usain Bolt or Iga Swiatek have picked up issues through their sporting careers, despite having elite support teams behind them. Unfortunately injuries do just happen, but with foresight, preparation and providing the best nutritional support to their horses, trainers will give themselves the greatest chance of avoiding yet another bad news phone call to an owner.

Train, Race, Recover and Repeat – How targeted nutrition can support the recovery process to optimise performance

Article by Dr Andy Richardson BVSc CertAVP(ESM) MRCVS

Introduction

Horses evolved as herd-living herbivores with a digestive tract designed to cope with a near continuous dietary input of forage in the form of a wide range of plant species. A large hindgut acts as a fermentation vessel where gut microbiota (predominantly a mix of bacteria, protozoa and fungi) exist in harmony with the horse in order to digest the fibre rich plant material.

Fibre is important to the horse for several reasons. The digestion of fibre releases energy and other key nutrients to the horse. Fibre also acts to provide bulk in the digestive tract, thus helping maintain the passage of faecal material through the system. Fibre also acts like a sponge to absorb water in the gut for release when required.

As horses became domesticated and used for work or sporting purposes, more energy-dense feeds in the form of cereal grains were introduced to their diet, as simple forage did not provide for all the caloric requirements. Cereal grains are rich in starch, which is an energy-dense form of nutrition. However, too much starch can cause problems to a digestive tract that remains designed for a pasture-based diet. The issues that can be caused by the trend away from a solely pasture-based diet can be digestive, behavioural or clinical.

Nonetheless, the combination of forage and cereal-based concentrates remains the mainstay approach for the majority of horses in training today, in order to maximise performance. A great deal of research and expertise are utilised by the major feed companies to ensure that modern racehorse concentrate feeds provide adequate provision of the major nutrients required and minimise unwanted effects of starch in the diet.

This article aims to discuss some scenarios where targeted or supplemented nutrition can act to help overcome some of the nutritional challenges faced by the modern horse in training, as they “Train, Race, Recover and Repeat.”

Equine Gastric Ulceration Syndrome (EGUS)

EGUS occurrence in racehorses is well documented, with prevalence shown to be over 80% in horses in training (Vatistas 1999). With a volume of approximately 2–4 gallons (7.53–15 litres), the stomach in horses is relatively small compared to their overall size due to its functional role in accommodating trickle feeding that occurs during their natural grazing behaviour. 

As a horse chews, it produces saliva, which is a natural buffer for stomach acid. When the horse goes for a period of time without chewing, the production of saliva ceases, and stomach acid is not as effectively neutralised. The lower half of the stomach is better protected from acid due to its more resistant glandular surface. The upper, or squamous, region does not have such good protection, however, and this can be a problem during exercise when acid will physically splash upwards, potentially leading to gastric ulceration.

In practice, this can presentrepresent a challenge for horses in training. Typically, they will be fed a concentrate-based feed in the early morning that stimulates a large influx of acid in order to help digest the starch. This may be followed by a period without ad-lib access to hay, thus reducing the amount of saliva subsequently produced to act as a buffer. When the horse is subsequently worked, there is a risk of acid damaging the upper squamous region of the stomach. There is some evidence to suggest that the provision of hay in advance of exercise may act like a sponge for the acid, as well as helping form a fibrous matt to minimise upward splash.

Gastric ulceration can go undetected in horses in training and may not lead to any obvious clinical signs. In other horses, it can lead to colic, poor appetite, dull coat and behavioural changes. In both scenarios, it is likely that the ulceration will have an impact on their performance, with decreased stride length, reduced stamina and inability to relax at speed all being possible consequences (Nieto 2009). Gastric ulceration can therefore have a significant impact on the ability of a horse to perform optimally day in day out in a training environment. This is exacerbated when ulceration leads to a reduction in appetite, with the obvious downside of a reduction in calorie intake leading to condition loss and further drop in performance.

This is an area where targeted nutrition has been clinically proven to play an important role. Ingredients such as pectin, lecithin, magnesium hydroxide, live yeast, calcium carbonate, zinc and liquorice have all been studied as having beneficial effects on gastric ulceration (Berger 2002, Loftin 2012, Sykes 2013). It is likely that a combination of the active ingredients will be most efficacious, with benefits noted when the supplement is added to the feed ration to help neutralise acid and form a gel-like protective coating on the stomach surface.

The daily administration of a targeted gastric supplement can be an important part of daily nutrition of the horse in training, alongside the use of pharmaceuticals such as omeprazole or esomeprazole when required.

Sweat loss

Horses have one of the highest rates of sweat loss of any animal, with sweat being comprised of both water and electrolyte ions such as sodium, potassium, chloride, magnesium and calcium. Therefore, it is not surprising that horses in training are at risk of unwanted issues should sweat loss not be replaced.

It is also worth noting that transportation can also lead to excessive sweat loss, with studies showing sweat rates of 5 litres per hour of travel on a warm day (van den berg 1998).

If the electrolytes lost in sweat are not adequately replaced, a drop in performance can result, as well as clinical issues such as thumps, dehydration and colic.

Electrolytes play key roles in the contraction of muscle fibres and transmission of nerve impulses. Horses without adequate electrolyte levels are at risk of early onset fatigue that may result in reduced stamina. It is also worth noting that horses that train on furosemide will have higher levels of key electrolyte losses, so will require targeted support to help maintain performance levels (Pagan 2014).

There is also evidence to suggest that pre-loading of electrolytes may be beneficial (Waller 2022). For horses in daily work, the addition of electrolytes to the evening feed will not only replace losses but also help optimise levels for the following day’s travel or race. The benefit of providing electrolytes with feed is that it will minimise the risk of the electrolyte salts irritating the stomach lining, which can occur if given immediately after exercise on an empty stomach. Feeding electrolytes when the horse is relaxed back in the stable will also allow them to drink freely, with the added benefit that electrolytes will stimulate the thirst reflex when they are relaxed, ensuring they are adequately hydrated for the following day.

Products should be chosen on the basis of adequate key electrolyte provision as not all products will provide meaningful levels of all the key electrolyte ions.

Muscle soreness

The process of muscle breakdown and repair is a normal adaptive response to training. This process can lead to inflammation and soreness or stiffness after exercise. In humans, there is a well-recognised condition called Delayed Onset Muscle Soreness (DOMS).

Further research is required to fully understand the impact of DOMS in horses. DOMS is the muscular pain that develops 24–72 hours after a period of intense exercise. There is no pain felt by the muscles at the time of exercise, in contrast to a ‘torn muscle’ or ‘tying-up’ for example.

In humans, DOMS is thought to be the result of tiny microscopic fractures in muscle cells. This happens when doing an activity that the muscles are not used to doing or have done it in a more strenuous way than they are used to.

The muscles quickly adapt to being able to handle new activities, thus avoiding further damage in the future; this is known as the “repeated-bout effect”. When this happens, the micro-fractures will not typically develop unless the activity has changed in some substantial way. As a general rule, as long as the change to the exercise is under what is normally done, DOMS are not experienced as a result of the activity.

In practice, avoiding any post-exercise muscle soreness in a training programme may be unavoidable, as exercise intensity and duration increases. Horses are far from being machines, so there is a fine balance between a programme that gets a horse fit for purpose without some post-exercise muscle discomfort. Physiotherapy, swimming and turnout will all likely benefit horses experiencing muscle discomfort. Whilst non-steroidal anti-inflammatories will always have their place for horses in training, one area of advancement is the use of plant-based phytochemicals to support the anti-inflammatory response (Pekacar 2021). These may have the benefit of not leading to unwanted gastrointestinal side effects and not having prolonged withdrawal times, although this should always be checked with any supplement particularly with the recent update regarding MSM on the BHA prohibited substance list.

Exercise will also lead to a process of muscle cell damage caused by oxidative stress. This is an inflammatory process and recovery from oxidative stress is key to allow for muscle cell repair and growth. Antioxidants are compounds that help recovery and repair of muscle cells following periods of intense exercise. The process of oxidative stress in muscle cells can lead to muscle fatigue and inflammation if left unsupported. Antioxidant supplementation in the form of Vitamin E or plant-based compounds can help protect against excessive oxidative stress and support muscle repair after exercise (Siciliano 1997).

Conclusion

Nutritional management of horses in training is a complex topic, not least as every horse is an individual and so often needs feeding accordingly. Whilst there is a lot of science available on the subject, the ‘art of feeding’ a racehorse—something that trainers and their staff often have in-depth knowledge of— remains an incredibly important aspect. Targeted nutritional supplements undoubtedly have their place, as discussed in, but not limited to, the scenarios above. 

Veterinarians, physiotherapists, other paraprofessionals and nutritionists all play a role in minimising health issues and maximising performance. In the quest for optimal performance on the track, nutritional support is one of the cornerstones of the ‘marginal gains’ theory that has long been adopted in elite human athletes. There is no doubt that racehorses themselves are supreme athletes that live by the mantra of Train, Race, Recover, and Repeat.

References

Berger, S. et al (2002). The effect of acid protection in therapy of peptic ulcer in trotting horses in active training. Pferdeheilkunde 27 (1), 26-30,

Loftin, P. et al (2012). Evaluating replacement of supplemental inorganic minerals with Zinpro Performance Minerals on prevention of gastric ulcers in horses. J.Vet. Int. Med. 26, 737-738

McCutcheon, L.J. and geor R.J. (1996). Sweat fluid and ion losses in horses during training and competition in cool vs. hot ambient conditions: implications for ion supplementation. Equine Veterinary Journal 28, Issue S22.

Nieto, J.E. et al (2009). Effect of gastric ulceration on physiologic responses to exercise in horses. Am. J. Vet. Res.70, 787-795.

Pagan, J.D. et al (2014). Furosemide administration affects mineral excretion in exercised Thoroughbreds. In: Proc. International Conference on Equine Exercise Physiology S46:4.

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Sykes, B. et al (2013). Efficacy of a combination of a unique, pectin-lecithin complex, live yeast, and magnesium hydroxide in the prevention of EGUS and faecal acidosis in thoroughbred racehorses: A randomised, blinded, placebo-controlled clinical trial. Equine Veterinary Journal, 45, 16.

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Waller, A.P., and M.I. Lindinger. (2022). Tracing acid-base variables in exercising horses: Effects of pre-loading oral electrolytes. Animals (Basel) 13(1), 73.

Equine Nutrition - be wary of false feeding economies

Article by Louise Jones

Many horses, especially performance horses, breeding stallions, and broodmares at certain stages of production, require additional calories in the form of hard feed. Whilst in the current economic climate, with rising costs and inflation, it might be tempting to look at lower cost feeding options; in reality, this could be a false economy. When choosing a feed, in order to ensure that you are getting the best value for money and are providing your horses with the essential nutrients they require, there are a number of factors to consider.

Quality 

The ingredients included in feed are referred to as the raw materials. These are usually listed on the feed bag or label in descending order by weight. Usually they are listed by name (e.g., oats, barley wheat) but in some cases are listed by category (e.g., cereals). Each raw material will be included for a specific nutritional purpose. For example, full-fat soya is a high-quality source of protein, whilst cereals such as oats are mainly included for their energy content, also contributing towards protein, fibre and to a lesser degree, fat intake.

Waste by-products from human food processing are sometimes used in the manufacture of horse feed. Whilst it is true that they do still hold a nutritional value, in most cases they are predominantly providing fibre but contain poor levels of other essential nutrients. Two of the most commonly used by-products are oatfeed and distillers grains. Oatfeed is the fibrous husks and outer layer of the oat and it mainly provides fibre. Distillers grains are what is left over after yeast fermentation of cereal grains used to produce alcohol. The leftover grain is dried and used in the feed industry as a protein source. Distillers grains can be high in mycotoxins, which are toxic chemicals produced by fungi in certain crops, including maize. Furthermore, despite being used as a protein source, distillers grains are typically low in lysine. As one of the first limiting amino acids, lysine is a very important part of the horse’s diet; horses in work, pregnant mares and youngstock all have increased lysine requirements.

Another ingredient to look out for on the back of your bag of feed is nutritionally improved straw, often referred to as “NIS”. This is straw that has been treated with chemicals such as sodium hydroxide (caustic soda) to break down the structural fibre (lignins) and increase its digestibility. Straw is a good example of a forage which contains filler fibre; in fact, you can think of it as the horse’s equivalent of humans eating celery. Traditionally, oat straw was used to make NIS, however many manufacturers now use cheaper wheat or barley straw due to the rising cost of good quality oat straw.  Not all companies state what straw is used and instead use generic terms such as cereal straw, which again, allows them to vary the ingredients used depending on cost and availability. 

By law, feed manufacturers must declare certain nutrients on the feed bag, one of which is the percentage crude protein. This tells you how much protein the feed contains. However, not all protein is created equal; some protein is of very high quality, whilst other proteins can be so low in quality that they will limit a horse’s ability to grow, reproduce, perform or build muscle. Protein ‘quality’ is often measured by the levels of essential amino acids (e.g., lysine, methionine) it contains. In most cases feed manufacturers do not have to list the amount of these essential amino acids; but looking at the ingredient list will give you a clue as to how good the protein quality is. Good sources of high-quality protein include legumes and soybean meal, whereas by-products often contain moderate- or low-quality protein, even though they may be relatively high in crude protein. 

Understanding more about the ingredients in your bag of horse feed will help you to assess whether they are providing good, quality nutrition. Feeds containing large proportions of lower quality ingredients will obviously be cheaper, but this could compromise quality of the products. The goal therefore is to ensure that the nutritional makeup of the products remains high quality and consistent. 

Cooking for digestibility 

Digestibility is a term used to describe the amount of nutrients that are actually absorbed by a horse and are therefore available for growth, reproduction, and performance. Understanding digestibility of energy sources—such as fibre, fat, starch, and sugar as well as protein, vitamin and mineral digestibility—is important when devising optimal diets for horses. 

Most of the energy in grains is contained in the starch; however, horses cannot fully digest starch from uncooked (raw) grains in the small intestine, which results in this undigested starch traveling into the hindgut where it will ferment and potentially cause hindgut acidosis. Therefore, in order to maximise pre-caecal digestibility, feed manufacturers cook the grain. Similarly, soya beans must be carefully processed prior to feeding them to horses. This is because raw soybeans contain a specific enzyme that blocks the action of trypsin, an enzyme needed for protein absorption.

There are various methods of cooking including pelleting, micronizing, extrusion, and steam-flaking.  This is a fine art as, for example, undercooking soya beans will not deactivate the enzymes correctly, thus resulting in reduced protein absorption. On the other hand, overcooking will destroy essential amino acids such as lysine, methionine, threonine, and possibly others.

Variation in cooking methods, and hence digestibility, can have a direct impact on how the finished product performs. Your individual feed manufacturer should be able to tell you more about the cooking processes they use to maximise digestibility.

Micronutrient and functional ingredients specification

The back of your bag of feed should list the inclusion of vitamins, such as vitamin E, and minerals including copper and zinc. A lower vitamin and mineral specification is one way feed companies can keep the cost of their products down. For example, the vitamin E level in one unbranded Stud Cube is just 200 iu/kg—50% lower than in a branded alternative.

For most vitamins and minerals, the levels declared on the back of the bag/label only tell the amount actually added and do not include any background levels provided by the raw materials. In other marketing materials, such as brochures, some companies will combine the added figure with the amount provided by other raw materials in order to elevate the overall figure. For example, a feed with 50 mg/kg of added copper may list the total copper as 60 mg/kg on their website or brochure.  Whilst it is perfectly acceptable to do this, it is equally important to recognise that background levels in different raw materials can vary and hence should not be relied upon to meet requirements. To complicate this slightly further, chelated minerals (e.g., cupric chelate of amino acids hydrate, a copper chelate) may be included. Chelated minerals have a higher bioavailability, and so a feed with a high inclusion of chelated copper may perform as well as one that has an even higher overall copper level but does not include any chelates.

Equally important is the need to verify that any specific functional ingredients such as prebiotics or yeast are included at levels that are likely to be efficacious. 

Feeding rates

Whilst the cost of a bag of feed is undeniably important, another aspect that should be considered is the amount of feed required to achieve the desired body condition and provide a balanced diet. Feeding higher volumes of hard feed not only presents a challenge from a gastrointestinal health point of view but also increases the cost per day of feeding an individual. For example, the daily cost of feeding 8kg of a feed costing £400/€460 per tonne vs 5¼ kg of a feed costing £600/€680 per tonne are exactly the same. Plus, the lower feeding rate of the more expensive product will be a better option in terms of the horse’s digestive health, which is linked to overall health and performance. To keep feeding costs in perspective, look at the cost of feeding a horse per day rather than relying on individual product prices.

Consistency 

When a nutritionist creates a recipe for a horse feed, they can either create a ‘set recipe’ for the feed or a ‘least cost formulation’. A set recipe is one that doesn’t change and will use exactly the same ingredients in the same quantities. The benefit of this is that you can rest assured that each bag will deliver the same nutritional profile as the next. However, the downside is that if the price of a specific ingredient increases, unfortunately, so will the cost of the product.

On the other hand, least-cost formulations use software to make short-term recipes based on the cost of available ingredients. It will use the cheapest ingredient available. When done correctly, they will provide the amount of calories (energy), crude protein, vitamins and minerals as specified on the label. However, the ingredients will change, and protein quality can be compromised. Often feed companies using least-cost formulations will print their ingredients on a label, rather than the bag itself, as the label can be amended quickly and cheaply, should they alter the recipe.

Checking the list of ingredients in your feed regularly should alert you to any formulation changes.  Equally look out for feeds that include vague ingredient listings such as ‘cereal grains and grain by-products, vegetable protein meals and vegetable oil’; these terms are often used to give the flexibility to change the ingredients depending on how costly they are.

Peace of mind

Another important issue is that some companies producing lower-cost feeds may not have invested in the resources required to carry out testing for naturally occurring prohibited substances (NOPS) such as theophylline, banned substances (e.g., zilpaterol - an anabolic steroid) or mycotoxins (e.g., zearalenone). It is true that, even with the most stringent testing regime, identifying potential contamination is difficult; and over recent years, a number of feed companies have had issues.  However, by choosing a feed manufacturer who is at the top of their game in terms of testing and monitoring for the presence of such substances will give you peace of mind that they are aware of the threat these substances pose, and they are taking significant precautions to prevent their presence in their products. It is important to source horse feed from a BETA NOPS registered feed manufacturer at a minimum. It may also be prudent to ask questions about the feed manufacturer’s testing regime and frequency of testing.  

Supplements – to use or not to use?

A good nutritionist will be able to assess any supplements that are fed, making note of why each is added to the diet and the key nutrients they provide. It is easy to get stuck into the trap of feeding multiple supplements that contain the same nutrients, effectively doubling up on intake. Whilst in many cases this isn’t nutritionally an issue, it is an ineffective financial spend. For example, B vitamins can be a very useful addition to the diet, but if provided in levels much higher than the horse needs, they will simply be excreted in the urine. Reviewing the supplements you are feeding with your nutritionist to ensure they are essential and eliminating nutritional double-ups is one of the simplest ways to shave off some expense.

Review and revise

A periodic review of your horse’s diet ensures that you’re providing the best nutrition in the most cost-effective way. This will require the expertise of a nutritionist. Seeking advice on online forums and social media is not recommended as this can lead to misinformed, biased advice or frankly, dangerous recommendations. On the other hand, a properly qualified and experienced nutritionist will be able to undertake a thorough diet evaluation, carefully collecting information about forages, concentrates, and supplements. 

Working with a nutritionist has many advantages; they will be able to work with you to ensure optimal nutrition, whilst also helping to limit needless expenses. Some nutritionists are better than others, so choose wisely. (Does the person in question have the level of qualifications?) Bear in mind that while qualifications can assure you that the nutritionist has rigorous science-based training, experience is also exceptionally important. Ask them about their industry experience and what other clients they work with to ensure they have the right skill set for your needs. In addition, a competent nutritionist will be willing and able to interact with your vet where and when required to ensure that the health, well-being, and nutrition of your horses is as good as it can be. 

There are independent nutritionists available, but you will likely incur a charge—often quite a significant one. On the other hand, the majority of feed companies employ qualified, experienced nutritionists and offer their advice, free of charge.

Nutrition and the new science of the "Gut-Brain connection"

Article by Scott Anderson

Trainers are always looking to gain an edge in performance. But what about their mental state? Are they jittery, distracted or disinterested? No matter how strong the horses, their heads must be in the game to succeed.

Surprisingly, much of that mental attitude is driven by gut health, which in turn depends on the collection of microbes that live there: the microbiota. In a horse, the microbiota is a tightly packed community of about 100 trillion microbes, composed of bacteria, archaea, fungi and protozoa. It colonises the entire GI tract but is largely concentrated in the hindgut, where it works to ferment the prebiotic fibre in forage. The microbial fermentation of fibre into fatty acids produces 70% of the animal’s energy requirements and without it, the horse couldn’t get sufficient energy from simple forage. Intriguingly, byproducts of that fermentation can affect the brain. 

It is easy to be sceptical about this gut-brain connection, but over the last decade, research has made it clear that gut microbes have an outsized influence on mood and behaviour. Microbes that improve mental state are called psychobiotics, and they may completely change the way you train and manage your horses. A horse’s health – and consequently its performance – starts in the gut.

Inflammation

When the microbiota is unbalanced by stress, diet or sickness, it is said to be dysbiotic. It loses diversity, and a handful of bacterial species compete for domination. Without the pushback of a diverse population, even beneficial bacteria can become pathogenic. Surprisingly, that can affect the brain. Multiple studies in various animal models have shown that transmitting faecal matter from one animal to another also transmits their mood. This demonstrates that a dysbiotic microbiota can reliably cause mental issues including anxiety and depression, thereby affecting performance. 

An important function of the microbiota is to fight off pathogens by outcompeting, starving or killing them. However, a dysbiotic microbiota is less diligent and may permit pathogens to damage the gut lining. A degraded gut lining can leak, allowing bacteria and toxins into the bloodstream. The heart then unwittingly pumps them to every organ in the body, including the brain. This makes the gut the primary source of infection in the body, which explains why 80% of the immune system is located around the intestines. Over time, a leaky gut can lead to chronic systemic inflammation, which weakens the blood-brain barrier and interferes with memory, cognition and mood. 

Inflammation is a major component of the gut-brain connection, but not the only one.

Neurotransmitters and hormones

Horses and humans use neurotransmitters to communicate between nerve cells. Brains and their attendant nerve bundles constitute a sophisticated network, which makes it somewhat alarming that microbes also produce neurotransmitters. Microbes use neurotransmitters to converse with each other, but also to converse with their host. The entire gut is enmeshed in nerve cells that are gathered up into the vagus nerve that travels to the brain. Microbial neurotransmitters including serotonin and dopamine thus allow certain microbes to communicate directly with the brain via the vagus nerve. We know this happens with specific bacteria, including Lactobacillus species, because when the vagus is severed, their psychobiotic effects disappear. 

As well as neurotransmitters, hormones are involved in gut-brain communications. The hypothalamus-pituitary-adrenal (HPA) axis controls the stress response in animals. The hypothalamus is located low in the brain and responds to stressors – such as a lurking predator – by producing hormones that stimulate the neighbouring pituitary, which then triggers the adrenal gland to produce cortisol, the stress hormone. Cortisol acts as a threat warning and causes the horse to ramp up glucose production, supplying the energy needed to escape a predator. This is the same hormonal circuit that trainers exploit for racing.

The HPA axis produces cortisol in response to stress. Cortisol inhibits the immune system, which in combination with a leaky gut allows pathogens to enter the bloodstream. Susequent systemic inflammation and vagal feedback lead to stereotypies.

The production of these hormones redirects energy to the heart, lungs and muscles at the expense of the immune system. From an evolutionary point of view, the tradeoff makes sense: first escape the predator and deal with infections later. After the danger has passed, cortisol causes the HPA to return to normal – the calm after the storm. 

However, continued stress disrupts that cycle, causing anxiety and diminishing the brain’s ability to store memories. This can dramatically interfere with training. Stress can also induce the release of norepinephrine, which promotes the growth of pathogenic bacteria including Campylobacter jejuni, Listeria, Helicobacter pylori, and Salmonella. Prolonged high cortisol levels can increase gut leakiness, potentially leading to infection and further compounding the situation. In the long term, continued stress leads to systemic inflammation, which is a precursor to problematic behaviours.

Short-chain fatty acids

When microbes consume proteins and fibre, they break them down into their constituent molecules, such as amino acids, fatty acids and sugars. These are the metabolites of the microbes. As well as neurotransmitters and hormones, the gut-brain conversation is mediated by metabolites like butyrate, an important short-chain fatty acid which plays multiple roles in the body. 

In the gut, butyrate serves as a preferred nutrient for the cell lining. It encourages the differentiation of stem cells to replenish gut cells that are routinely sloughed off or damaged. It plays an important role in the production of mucus – an essential part of gut protection – which coats the gut from mouth to anus. In the muscles, butyrate boosts the growth of skeletal muscle, crucial to athletic performance, as well as inducing the production of glucose, the primary muscle fuel. One-quarter of systemic glucose is driven by butyrate. In its gut-brain role, butyrate passes through the blood-brain barrier, where it nourishes and enhances the growth of new brain cells. 

These factors make butyrate a star player in the gut-brain connection. They also highlight the benefits of prebiotic fibre, especially when high-energy, low-fibre feeds are provided.

Starting a microbiota

We’ve explored the major pathways of the gut-brain connection: inflammation, neurotransmitters, hormones and fatty acids. Some of these pathways are at odds with each other. How does such a complicated system come together?

As mentioned, the microbiota is an animal’s first line of defence against pathogens, attacking and killing them often before the immune system is even aware of them. That means a healthy microbiota is an essential part of the immune system. However, the immune system is designed to attack foreign cells, which includes bacteria. For the microbiota to survive, the immune system must therefore learn to accept beneficial microbes. This lesson in tolerance needs to take place early in the foal’s development, or its immune system may forever fight its microbiota.

There are multiple ways nature ensures that foals get a good start on a microbiota that can peacefully coexist with the immune system. The first contribution to a protective microbiota comes from vaginal secretions that coat the foal during birth. After birth, microbes are included in the mare’s milk. These microbes are specially curated from the mare’s gut and transported to the milk glands by the lymphatic system. Mare’s milk also includes immune factors including immunoglobulins that help the foal to distinguish between microbial friends and foes. An additional way to enhance the microbiota is through coprophagia, the consumption of manure. Far from an aberration, foals eat their mother’s manure to buttress their microbiota. 

Microbes affect the growth and shape of neurons in various brain sites as the foal develops – a remarkable illustration of the importance of a healthy early gut microbiota. 

The cooperation between the immune system and the microbiota is inevitably complex. Certain commensal bacteria, including Clostridiales and Verrucomicrobia, may be able to pacify the immune system, thus inhibiting inflammation. This is a case where microbes manage the immune system, not the other way around. These convoluted immune-microbial interactions affect the mental state – and consequently the behaviour – of the horse, starting at birth.

Stereotypies

A 2020 study of 185 performance horses conducted by French researchers Léa Lansade and Núria Mach found that the microbiota, via the gut-brain connection, is more important to performance than genetics. They found that microbial differences contributed significantly to behavioural traits, both good and bad. A diversified and resilient microbiota can help horses better handle stressors including stalling, training, and trailering. A weakened or dysbiotic microbiota contributes to bad behaviours (stereotypies) and poor performance. 

The horses in this study were all carefully managed performance horses, yet the rates of stereotypies were surprisingly high. A kind of anxiety called hypervigilance was observed in three-quarters of the horses, and almost half displayed aggressive behaviour like kicking or biting. 

The study found that oral stereotypies like biting and cribbing were positively correlated with Acinetobacter and Solibacillus bacteria and negatively correlated with Cellulosilyticum and Terrisporobacter. Aggressive behaviour was positively correlated with Pseudomonas and negatively correlated with Anaeroplasma. 

Some of these behaviours can be corrected by certain Lactobacillus and Bacteroides species, making them psychobiotics. That these personality traits are correlated to gut microbes is truly remarkable. 

Intriguingly, the breed of a horse has very little impact on the makeup of its microbiota. Instead, the main contributor to the composition of the microbiota is diet. Feeding and supplements are thus key drivers of the horse’s mental state and performance. 

The gut-brain connection and training

How might the gut-brain connection affect your training practices? Here are some of the unexpected areas where the gut affects the brain and vice-versa:

High-energy feed. Horses evolved to subsist on low-energy, high-fibre forage and thus have the appropriate gut microbes to deal with it. A high-energy diet is absorbed quickly in the gut and can lead to a bloom in lactic acid-producing bacteria, which can negatively impact the colonic microbiota. High-energy feeds are designed to improve athletic output, but over time, too much grain can make a horse antisocial, anxious and easily spooked. This can damage performance—the very thing it is trying to enhance. Supplementary prebiotics may help to rebalance the microbiota on a high-starch regimen.

Changing feed regimens quickly. When you change feed, certain microbes will benefit, and others will suffer. If you do this too quickly, the microbiota can become unbalanced or dysbiotic. Slowly introducing new feeds helps to prevent overgrowth and allows a balanced collection of microbes to acclimate to a new regimen. 

Stress. Training, travelling and racing all contribute to stress in the horse. A balanced microbiota is resilient and can tolerate moderate amounts of stress. However, excessive stress can lead, via the HPA axis, to a leaky gut. Over time, it can result in systemic inflammation, stereotypies and poor performance.

Overuse of antibiotics. Antibiotics are lifesavers but are not without side effects. Oral antibiotics can kill beneficial gut microbes. This can lead to diarrhoea, adversely affecting performance. The effects of antibiotics on the microbiota can last for weeks and may contribute to depression and anxiety. 

Exercise and training. Exercise has a beneficial effect on the gut microbiota, up to a point. But too much exercise can promote gut permeability and inflammation, partly due to a lack of blood flow to the gut and consequent leakiness of the intestinal lining. Thus, overtraining can lead to depression and reduced performance.

Knowing how training affects the gut and how the gut affects the brain can improve outcomes. With a proper diet including sufficient prebiotic fibre to optimise microbiota health, a poor doer can be turned into a model athlete. 

References

Mach, Núria, Alice Ruet, Allison Clark, David Bars-Cortina, Yuliaxis Ramayo-Caldas, Elisa Crisci, Samuel Pennarun, et al. “Priming for Welfare: Gut Microbiota Is Associated with Equitation Conditions and Behavior in Horse Athletes.” Scientific Reports 10, no. 1 (May 20, 2020): 8311.

Bulmer, Louise S., Jo-Anne Murray, Neil M. Burns, Anna Garber, Francoise Wemelsfelder, Neil R. McEwan, and Peter M. Hastie. “High-Starch Diets Alter Equine Faecal Microbiota and Increase Behavioural Reactivity.” Scientific Reports 9, no. 1 (December 9, 2019): 18621. https://doi.org/10.1038/s41598-019-54039-8.

Lindenberg, F., L. Krych, W. Kot, J. Fielden, H. Frøkiær, G. van Galen, D. S. Nielsen, and A. K. Hansen. “Development of the Equine Gut Microbiota.” Scientific Reports 9, no. 1 (October 8, 2019): 14427.

Lindenberg, F., L. Krych, J. Fielden, W. Kot, H. Frøkiær, G. van Galen, D. S. Nielsen, and A. K. Hansen. “Expression of Immune Regulatory Genes Correlate with the Abundance of Specific Clostridiales and Verrucomicrobia Species in the Equine Ileum and Cecum.” Scientific Reports 9, no. 1 (September 3, 2019): 12674. 

Daniels, S. P., J. Leng, J. R. Swann, and C. J. Proudman. “Bugs and Drugs: A Systems Biology Approach to Characterising the Effect of Moxidectin on the Horse’s Faecal Microbiome.” Animal Microbiome 2, no. 1 (October 14, 2020): 38.

Probiotics as an alternative to antibiotics to reduce resistance in the gut

Article by Kerrie Kavanagh

The leading causes of horse mortality can be attributed to gastrointestinal diseases. Therefore, maintaining the balance of the gut microbiota and avoiding a shift in microbial populations can contribute to improved health status. The gut microbiota, however, can be influenced by countless dynamic events: diet, exercise, stress, illness, helminth infections, aging, environment and notably, antimicrobial therapy (antibiotics). These events can lead to gut dysbiosis—a fluctuation or disturbance in the population of microorganisms of the gut, which can contribute to a wide range of disease. The use of antibiotics in horses is thought to have one of the most notable effects on the gut microbiota (gut dysbiosis), which can lead to diseases such as colitis, colic and laminitis.

Antibiotics, which are antimicrobial agents active against bacteria, are important to equine medicine; and bacterial infections can be resolved quite successfully using antibiotics for antimicrobial therapy, but there are consequences to their use. An antimicrobial agent can be defined as a natural or synthetic substance that kills or inhibits the growth of microorganisms such as bacteria, fungi and algae. One of the consequences of antibiotic use is that of antibiotic-associated diarrhoea, which can contribute to poor performance in the horse and even mortality. In antimicrobial therapy, the target organism is not the only organism affected by the antimicrobial agent but also the commensal microbiota too (the normal flora of the equine gut). Antibiotics can promote fungal infections and resistant organisms and impede or even eliminate the more sensitive organisms; and they can have both short and long-term consequences on the gut microbiota composition and function. 

Research has indicated that antibiotic treatment may adversely affect metabolic function in the gut by decreasing protein expression responsible for biochemical pathways such as glycolysis, iron uptake, glutamate hydrolysis and possibly even more metabolic functions. The use of antimicrobial drugs directly impacts and possibly contributes to the most notable effect on the gut microbiota of the host, leading to gut dysbiosis; and certain antibiotics can have further-reaching consequences on the microbiota than others. The type of antibiotic and mode of action (bacteriostatic versus bactericidal) will differ in their influences on the gut microbiota composition, e.g., clindamycin operates a bacteriostatic mode of action by inhibiting protein synthesis and exerts a larger impact on the gut microbiota compared to other antimicrobials. These influential consequences that are imparted by the antimicrobial agent are relatively yet to be elucidated and may result in the manifestation of illness or conditions later in life. For example, the development of asthma in humans has been linked to antibiotic treatment in early childhood as a result of bacterial infections. It may yield interesting results if researchers were to examine the gut microbiome of horses suffering from chronic obstructive pulmonary disease (COPD) and other chronic respiratory illnesses and to establish if there is indeed a link with antibiotic therapy used in horses from an early age. 

In comparison to the vast wealth of human studies conducted so far, the volume of equine studies falls disappointingly far behind, but that is changing as researchers focus their interest on developing and filling this gap of knowledge. One such study which examined the effect of antibiotic use on the equine gastrointestinal tract, demonstrated a significant reduction in culturable cellulolytic bacteria (>99%) from equine faeces during the administration period of trimethoprim sulfadiazine and ceftiofur in a study comparing responses to antibiotic challenge. That reduction was still evident at the end of the withdrawal period when compared to the control group. In other words, there was a significant reduction in the ‘normal’ bacteria of the gut. The ability of antibiotics to modulate the gut microbiota was evidenced by the proliferation of pathogenic Salmonella and Clostridia difficile (commonly associated with diarrhoea in horses) in the antibiotic challenged horses. This trend of reduction in cellulolytic bacteria associated with antibiotic use was also mirrored in a relatively recent study conducted in 2019, where a short-term reduction in culturable cellulolytic bacteria was combined with a progressive increase in amylolytic bacteria. The heavy reliance on cellulolytic bacteria in the role of equine digestion (without these types of bacteria the horse cannot break down their food) may, therefore, adversely affect the dietary energy available from forage during antimicrobial therapy and may therefore impact performance.

Another study that compared the effect of penicillin, ceftiofur and trimethoprim sulfadiazine (TMS) on the gut microbiota in horses using next-generation sequencing showed that TMS had the most profound impact on the microbiota, in particular the phylum Verrucomicrobia. This same study also reported a significant decrease in bacterial richness and diversity of the faecal microbiota. A reduction in bacterial diversity is certainly a trend that is commonly seen in gastrointestinal disease in horses. The restoration of the normal gut microbiota after completion of antibiotic treatment can take up to 40 days, but the organisational structure of the bacterial populations can take many years to re-establish the original structure map that was laid out in the gut pre-antibiotic treatment. 

The equine studies certainly show similarities to the human studies, indicating the consequences of antibiotics that can be seen across more than one species. Human studies have reported long-term consequences of antibiotic treatment on the human microbiota. One such human study investigated a 7-day clindamycin treatment and monitored the patients for two years. The impact on the human microbiota remained evident two years post-treatment, where a reduction in bacterial diversity and detection of high-resistance to clindamycin were detected. 

Interestingly, no resistant clones were detected in the control group over the two-year sampling period. Another study focusing on the effects of antibiotic treatment for Helicobacter pylori showed findings mirrored in similar studies of that field. The findings demonstrated the rapidly reducing bacterial diversity (one week) after antibiotic treatment and found that disturbances in the microbiota and high levels of macrolide resistance were evident four years post-treatment. Human studies may predict that equine studies will find similar trends with equine antimicrobial therapy. These studies highlight the impact of antibiotic use and the long-term persistence of antibiotic resistance remaining in the intestinal microbiome, which is a concern for both humans and animals. 

Antibiotics can lead to the selectivity and proliferation of resistant bacteria, which is evidenced by the long-term effects observed on the gut microbiota harbouring drug-resistant encoded genes. Horizontal gene transfer (HGT) commonly occurs in the gut (can be up to 25 times more likely to occur in the gut than in other environments). HGT can be attributed to the close proximity of the microbiota in the gut, allowing the transfer of genetic material via routes such as plasmids and conjugation; in other words, the bacteria in the gut have developed a pathway to transfer antibiotic resistant genes from one generation to another. Resistance to antibiotics is now a global issue for the treatment of many diseases. 

With the unfavourable association tied to Clostridium difficile infections (CDI) and the onset of colitis particularly in mature horses treated with β-lactam antibiotics (commonly used for equine infections), the incidences in which antimicrobial therapy is considered should be minimised and only used if entirely necessary. The use of broad-spectrum antibiotics in recurrent presentations of symptoms of disease such as urinary tract infections in humans or diarrhoea as a result of CDI in both humans and horses is promoting drug resistance.

The antibiotics, by disrupting the gut microbiota (which act as a defence against the establishment and proliferation of such pathogenic bacteria) are allowing the opportunity of growth for these multi-resistant microorganisms such as C. difficile, vancomycin-resistant enterococci (VRE), and multi-resistant Staphylococcus aureus (MRSA). The organism C. difficile and its antibiotic resistance has been demonstrated in the treatment of CDI for both humans and animals. The introduction of vancomycin (a glycopeptide antibiotic) in 1959 for the control of CDI remained effective until the 1990s when a more virulent form of C. difficile emerged. This new form of C. difficile with reported broad-spectrum antibiotic resistance resulted in chronic conditions and increased human mortality. C. difficile is most noted with human hospital-acquired infections. C. difficile BI/NAP1/027 has been shown to have resistance to fluoroquinolone antibiotics, moxifloxacin and gatifloxacin, which was not seen in historical genotypes. As C. difficile infections are found to cause gastrointestinal disease in horses as well as humans, this is certainly of concern.

Alternative therapies to antibiotic therapy to restore or modulate the gut microbiome after a gut dysbiosis event could be considered in certain circumstances where antibiotics are no longer effective (e.g., CDI), nor may they not be the best course (presence of Extended-spectrum -β-lactamase producing (ESBL) organisms) nor essential for example, when the diagnosis of the bacterial cause is uncertain. The rationale to using probiotic treatment along with antimicrobial treatment is that the antibiotic will target the pathogenic bacteria (e.g., C. difficile) and also the commensal microbiota of the gut, but the probiotic bacteria will help to re-establish the intestinal microbiota and in-turn prevent the re-growth of the pathogenic bacteria in the case or residual spores of C. difficile surviving the antibiotic treatment. Alternative therapies such as faecal microbiome transplant (FMT) or probiotic solutions can reduce the risk of proliferation of antibiotic-resistant bacteria and also have fewer implications on the gut microbiome as evidenced by antibiotic use. 

Probiotics have been defined by the Food and Agricultural Organisation (FAO) and the World Health Organisation (WHO) as “live non-pathogenic microorganisms that, when administered in adequate amounts, confer a health benefit on the host”. The word ‘probiotic’ is Greek in origin, meaning, ‘for life’; and the term was coined by Ferdinand Vergin in 1954. While the mechanisms of action of probiotics are complex and require a deeper knowledge of the modulations of the gastrointestinal microbiota, and the health benefits due to their use are the subject of some debate, there is no doubt that probiotics are considered by many as a vital resource to human and animal health.   

The use of probiotics in animal production, particularly in intensive swine and poultry production, has increased in recent years, primarily as an alternative to the use of antimicrobials in the prevention of disease. The problem of antibiotic-resistance and antimicrobial residues in food-producing animals (the horse is considered a food-producing animal), as a result of historical antibiotic use with the corresponding reduction in antibiotic efficacy in humans, leads to having to look at more sustainable options such as probiotic use to combat disease. Probiotics in horses are predominantly used as a treatment modality in the gastrointestinal microbial populations to combat illnesses such as diarrhoea—to prevent diarrhoea (particularly in foals) or help improve digestibility.  Shifts or fluctuations in the microbial populations of the equine gastrointestinal tract have been associated with diseases such as laminitis and colic.  

Gut dysbiosis, as mentioned previously is, a fluctuation or disturbance in the population of microorganisms of the gut is now being recognised as a cause of a wide range of gastrointestinal diseases; and in horses, it is one of the leading causes of mortality. The ability of probiotics in conferring health benefits to the host can occur via several different mechanisms: 1) inhibiting pathogen colonisation in the gut by producing antimicrobial metabolites or by competitive exclusion by adhering to the intestinal mucosa preventing pathogenic bacteria attachment by improving the function and structure; 2) protecting or restabilising the commensal gut microbiota; 3) protecting the intestinal epithelial barrier; 4) by inducing an immune response.

It is known that there is a wealth of factors that will adversely affect the gut microbiome, antibiotics, disease, diet, stress, age and environment are some of these compounding contributors. To mirror one researcher’s words echoing from an era where antibiotics were used as growth promoters in the animal industry, “The use of probiotic supplements seeks to repair these deficiencies. It is, therefore, not creating anything that would not be present under natural conditions, but it is merely restoring the flora to its full protective capacity”. In the case of using concurrent antibiotic and probiotic treatment, this strategic tweaking of the microbiota could be used as a tool to prevent further disease consequence and perhaps help improve performance in the horse.

The benefits of probiotic use in horses have not been investigated extensively but as mentioned previously, they are now being focused upon by researchers in the equine field. The most common bacterial strains used in equine probiotic products are Lactobacillus, Bifidobacterium, Streptococcus, Enterococcus, Bacillus and yeast strains of Saccharomyces. Lactobacillus, Bifidobacterium and Enterococcus strains typically account for less than 1% of the microbiota large gastrointestinal populations.

Regulation is lacking regarding labelling of probiotic products, often not displaying content with clarification and quality control (such as confirmed viability of strain[s]) not excised with over-the-counter probiotic products. There is evidence to suggest that host-adapted strains of bacteria and fungi enjoy a fitness advantage in the gut of humans and animals.  Therefore, there may be an advantage in using the individual animal’s own bacteria as potential probiotics. Probiotics and antibiotics used concurrently could be the way to minimise the introduction of antibiotic-resistant bacterial strains in the gut, and in turn, protect future antibiotic efficacy. 

Electrolyte Balance – vital to the proper functioning of a racehorse's system

Words - Dr. Cath Dunnett

Electrolytes are essential components of the racehorse’s diet as they are vital to the proper functioning of the body’s basic physiological processes, such as nerve conduction, muscle contraction, fluid balance and skeletal integrity. The major electrolytes, sodium, potassium, chloride, calcium and magnesium are widely distributed within the body, but can be more concentrated in particular organs and tissues. For example, the level of potassium is very high in red blood cells but quite low in plasma, and the level of calcium in blood is low, but comparatively very high in bone and in muscle cells. The body has in-built mechanisms that work to maintain the correct electrolyte balance within the tissues, fluids and cells. These modify the absorption of electrolytes in the gut, or their excretion by the kidneys. These mechanisms are not foolproof however, and electrolyte loss through sweat can be a major issue for Thoroughbreds. The sweat of the equine athlete, unlike its human counterpart, is hypertonic; meaning that horse sweat contains higher levels of electrolytes than the circulating blood plasma. Consequently, the horse loses comparatively large quantities of electrolytes through sweating.

Although the electrolyte composition of equine sweat varies between individuals, on average a litre would contain about 3.5g of sodium, 6g of chloride, 1.2g of potassium and 0.1g of calcium. From this we can see that the majority of the electrolyte lost is in the form of sodium and chloride or ‘salt’. The amount of sweat produced on a daily basis and therefore the quantity of electrolytes lost differs from horse to horse and depends on a number of factors. As sweating is primarily a cooling mechanism, how hard a horse is working, i.e. the duration and intensity of exercise and both the temperature and humidity of the environment are all significant. Horses can easily produce 10 litres of sweat per hour when working hard in hot humid conditions. Stressful situations can also cause greatly increased sweating.

For example, during transport horses can lose a significant amount of electrolyte through sweating and the opportunity for replenishing this loss through the diet may be less as feeding frequency is reduced. Use of electrolyte supplements either in the form of powders or pastes is advocated before, during and after travel, especially over long distances. A number of air freight transport companies advise trainers to use a powdered electrolyte supplement added to the feed on a regular basis given for the 3 days prior to travel. As this helps offset much of the loss normally incurred during transport and subsequently the horses arrive at their destination in better shape. Electrolyte supplementation is a valuable attribute in the ongoing battle to reduce in-flight dehydration.

Electrolytes lost from the body in sweat must be replenished through the diet. All feeds, including forages, have a natural electrolyte content and in concentrate feeds this is usually enhanced by the addition of ‘salt’, which is sodium chloride. Forages such as grass, hay, haylage or alfalfa (lucerne) naturally contain a large amount of potassium, as can be seen from the table 1 below. In fact, 5kg of hay for example, would provide in the region of 75g of potassium, which largely meets the potassium needs of a horse in training. It is therefore questionable whether an electrolyte supplement needs to routinely contain very much potassium unless forage intake is low. Calcium is another important electrolyte, but it is lost in sweat in only very small amounts and its availability in the diet tends to be very good.

Calcium is particularly abundant in alfalfa with each kilogram of the forage providing nearly 1.5g of calcium. A kilo of alfalfa alone would therefore go a long way towards replacing the likely calcium loss through sweating. In addition, the calcium found in alfalfa is very ‘available’ to the horse in comparison to other sources, such as limestone. Calcium gluconate is another very available source of calcium, however, it has a relatively low calcium content compared to limestone (9% vs. 38%) and so much more needs to be fed to achieve an equivalent calcium intake. Interestingly, there is great variation between individual horses in their ability to absorb calcium, however, scientific studies carried out at Edinburgh Vet School showed that this variability was considerably less when a natural calcium source in the form of alfalfa was fed.

By far the most important electrolytes to add to the feed are sodium and chloride or ‘salt’. The levels of sodium and chloride found in forage are quite low and due to manufacturing constraints only limited amounts of salt can be added to traditional racing feeds. A typical Racehorse Cube fed at a daily intake of 5kg (11lbs) would provide only about 20g of sodium and 30g of chloride. As can be seen from table 2 this is a fair way short of meeting the daily requirements for these particular electrolytes by a racehorse in hard work.

It is therefore very important that supplemental sodium and chloride is fed. Ordinary table salt is by far the simplest and most economical electrolyte supplement, but the downside is the issue of palatability as the addition of larger quantities of salt to the daily feed can cause problems with horses ‘eating up’. As an alternative salt could be added to the water, but only when a choice of water with and without salt is offered. Salt should not be added to the water if it puts a horse off from drinking, as dehydration will become a problem.

Inadequate water intake can also contribute to impaction colic. Saltlicks are another alternative, although intake can be very variable and we rely on the horse’s innate ability to realise its own salt requirements, which is questionable. So addition to the feed is by far the best route for adding salt or electrolyte supplements to the diet. Splitting the daily intake between two or three feeds can reduce problems with palatability.

Mixing salt and Lo Salt can make another simple DIY electrolyte supplement in the proportion of for example 500g to 250g respectively. Salt is sodium chloride (NaCl), whilst Lo Salt contains a mixture of sodium chloride and potassium chloride (KCl). This formulation provides 3g of sodium, 6g of chloride and 1g of potassium per 10g measure. This DIY mixture will replace these electrolytes in the approximate proportions that they are lost in sweat. What are the implications of a racehorse’s diet containing too little or too much of an electrolyte and how can we assess this? An inadequate level of certain electrolytes in the diet in some horses may simply result in reduced performance. In other individuals, it can make them more susceptible to conditions such as rhabdomyolysis (tying up), or synchronous diaphragmatic flutter (thumps), both of which are regularly seen in horses in training. Conversely, an excess electrolyte intake is efficiently dealt with by the kidneys and is ultimately removed from the body via the urine.

Therefore, the most obvious effect of an excessive electrolyte intake is increased drinking and urination. For this reason, the use of water buckets rather than automatic drinkers is preferred, as whilst the latter are far more labour efficient, the ability to assess water intake daily is lost. Excessive electrolyte intake can also be a causative factor in diarrhoea and some forms of colic. There is also some recent evidence in the scientific press that suggests that repeated electrolyte supplementation might aggravate gastric ulcers. However, these early studies used an electrolyte administration protocol typical of that seen during endurance racing, rather than simply a daily or twice daily administration, which is more commonly used in racing.

Supplements that contain forms of electrolyte that dissolve more slowly in the stomach, however, may be less aggressive to the sensitive mucosa. Unfortunately blood levels of sodium, potassium, chloride or calcium are poor indicators of whether dietary intake is sufficient or excessive unless it is very severe. This is because the body has effective systems for regulating the levels of these electrolytes in blood within very tight physiological limits. A creatinine clearance test, which measures the electrolyte content of a paired blood and urine sample is a much more useful indicator of dietary electrolyte adequacy.

There are a large number of commercial electrolyte products available, with a wide range in the breadth of ingredients that they contain. Consequently, they vary enormously in the amount of electrolyte that they deliver per recommended daily dose, as can be seen in table 3. In addition, whilst some glucose or other carbohydrate can help improve palatability, its presence should not compromise the amount of electrolyte that is contained within the supplement. In humans, it is recognised that the uptake of sodium from the gut is improved in the presence of glucose, while this effect in horses has not been firmly established. Electrolyte paste products are also often used either before and or after racing or travel.

These products are useful as they allow rapid electrolyte intake even when feed eaten may be reduced following racing. These electrolyte pastes often provide a more concentrated form of supplement and it is extremely important to ensure that the horse has access to water immediately following their use. Failure to do this may mean that the concentration of electrolytes in the gut actually draws water from the circulating blood, which can exacerbate dehydration. Another disadvantage with paste supplements is that if they are not formulated well, with an appropriate consistency, they can be difficult to dispense from a syringe and the horse may also be able to spit most of the product out after administration.

Some simple rules of thumb for choosing a good electrolyte are that salt should be one of the first ingredients listed on pack, as all ingredients are listed in descending order of inclusion. Additionally, be wary of supplements that taste sweet, as they may contain a lot of carbohydrate filler and little electrolyte. Some electrolyte supplements also contain many superfluous ingredients such as vitamins and trace minerals. The inclusion of these latter ingredients is largely unwarranted and their presence could cause issues with oversupply if the electrolyte is multi-dosed daily. Some electrolyte products specifically marketed towards racing may also contain bicarbonate.

The theory behind its inclusion is sound as ‘milk shaking’, whilst outside the rules of racing, has some scientific validity. However, the limited amount of bicarbonate contained in such electrolyte supplements is unlikely to have the positive effect on performance attributed to the former practice. Other extra ingredients such as pre-biotics may be more useful as they may improve the absorption of some electrolytes. In Summary, electrolyte supplementation in one form or another is essential within a racing diet. Ensuring that you are using a good electrolyte supplement is important and the quantities fed must be flexible and respond to changes in the level of work, degree of sweating and climate.

Clean Water and horses - the importance of this often forgotten essential nutrient

Words - Alan Creighton

The Irish Equine Centre monitors the environment in over 200 racing yards across Europe. That monitoring package includes air quality, feed and fodder quality and storage, stable hygiene testing, and indoor exercise hygiene testing. A further major portion of that environmental monitoring package includes regular water sampling both at source and water directly from buckets or troughs. Water is the number-one nutrient fed to any animal, and it is often overlooked both in nutrient programmes and in the diagnosis of health issues resulting from poor performance of racehorses. We often hear the excuse that “Ah sure, horses drink from dirty puddles and ponds; and they seem fine.” That may be true and even OK for horses on farms, where horses are on a break or at pasture, but it’s OK not for high- level stressed racehorses. Anything that affects the gut flora or metabolism of a racehorse can have a negative effect on performance.

By weight, horses consume up to three times as much water as food per day. If the water contains toxins, high levels of minerals or any other environmental contamination, nutritional and performance problems can result.

Horses should consume enough water to replace what is lost through faeces, urine and importantly for racehorses, sweat particularly due to exercise. Water consumption will depend on several factors. These factors can be variable and include temperature, humidity, feed and fodder quality, type and amount of feed and fodder, exercise level, stage of fitness and health. The average daily consumption for a 500kg horse would be approximately 45 litres per day in normal, average weather conditions. The same horse, when in full training, could consume nearly three times that or up to 125 litres of water per day. When racehorses are carrying out their conditioning or fitness work following a long break, particularly in warm weather, the sweat production can increase further, which in turn increases the water and electrolyte requirements.

At this stage of conditioning, there is a fine balance between water and electrolyte concentration, which is essential for appropriate muscle contraction and also in the cooling down process of the horse. An imbalance or a depletion of electrolytes can lead to premature muscle fatigue, reduced stamina, muscle cramps, poor post exercise recovery and tying up. These facts further highlight the need to ensure an abundant, safe supply of water to racehorses. 

Contaminated water will impact the performance of both. This is something that may be overlooked in all types of horse management. High bacterial content in water can affect all animals, and in particular young stock and under-pressure racehorses. High iron content in water can cause severe gut upset in horses, which builds up over time. High levels of nitrate, nitrite and aluminium can also have a large negative impact on horses. Water quality in farm wells can fluctuate greatly and require constant monitoring.

There are three main sources of water available to racehorses: mains or municipal water, well or borehole water and finally running water in streams, if using outdoor paddocks daily. Yards in or close to towns usually draw their water from a public or municipal system that provides extensive purification and filtration services and also regularly tests its water for contaminants such as disease-causing bacteria and toxic chemicals including pesticides. The worries are less from this source but not eliminated. If there is damage to the delivery line or a problem with the plumbing on your own yard or farm, your water could still be compromised. Mains water can also be variable in the concentration of fluoride and chlorine, which means it requires regular monitoring as this may affect the palatability of water.

If your drinking water comes from a small group scheme or your own private well, then you are responsible for ensuring it is safe to drink. Many wells provide beautifully clean water, but there is also the potential for contamination. Man-made water sources are not free of issues; they require consistent maintenance.

Wells which are drilled correctly, sealed and more than 50 feet (15m) deep have less chance of becoming contaminated with bacteria. Water from an old or shallow well should be tested more frequently. Wells close together can supply water of varying quality. Even two wells side by side can draw water from separate aquifers (underground water sources) and yield very different results. Water quality from wells, both in terms of bacterial content and physical and mineral makeup, can vary greatly based on seasonal factors. Drought, heavy rainfall, local farming practices all can have a negative impact.

Trainers more and more are seeing the benefits of keeping racehorses in outdoor paddocks either for a portion of the day or permanently. If the water source is only a stream or river, then obviously a good flow is required. Ponds are usually problematic. Agricultural chemicals and other environmental contaminants can cause blue-green algae to bloom in the water. Not all algae produce harmful chemicals, but blooms are indicators of unhealthy or stagnant water.

Horse owners often forget to observe or clean water troughs in paddocks. If the water in a trough appears green or murky, it needs to be dumped and replaced. When cleaning a water trough, it is often necessary to remove algae by more vigorous means than rinsing alone. Stiff brushes and apple cider vinegar are two safe tools for removing algae and discouraging regrowth. 

Like us, however, their water intake can quickly be adversely affected if the water’s taste is unpleasant. Horses that refuse to drink from unfamiliar-tasting water sources are distressingly common. There is more and more evidence to suggest that horses are reluctant to drink low pH or acidic water. You may have a scenario where a horse is used to drinking a balanced pH water (6.5-7.5) and then travels to a racetrack were the pH may be much lower (4.5-5.5) and then refuse to drink, which would be a problem and lead to dehydration if stabled there for a number of days.

The most common problem we find in water is bacterial contamination. Testing your well’s water for bacterial contamination on a regular basis is sound practice. A total coliform test checks the water for bacteria normally found in the soil, surface water, and human and animal waste. Coliform bacteria are not, in themselves, considered harmful, but their presence in your water supply is an indication that your well or supply may be contaminated either from runoff from a manure pit, a nearby septic tank, or fertiliser or manure spread on a nearby farm. Coliform levels can vary greatly due to drought conditions or with sudden heavy rainfall. It’s also possible to have high coliform levels when the well has developed physical defects, such as a broken or missing cap that could allow debris, surface water, insects or rodents inside. Bacterial testing is a good idea whenever there is a noticeable change in the colour, odour or taste of your water, or if a group of animals become sick. 

If high coliform levels turn up in your well water, it’s possible your own manure management is the culprit. To protect your water, make sure you situate your manure pit in an elevated, well-drained location, not on the lowest spot on the property. After a rainstorm, watch the flow of water—it should go around your manure pile, not through it. Simply rerouting the flow of run-off water can improve your water quality considerably. 

The variability of bacterial levels in water supplies often results in trainers needing to install a UV filter onto the water inlet pipe, which feeds their yard. UV filters, once working correctly and maintained, are effective at reducing the bacterial load.

Blue-green algae in natural water sources can produce cyanotoxins, which are extremely dangerous for horses. Blue-green algae poisoning can cause muscle tremors, laboured breathing, bloody diarrhoea, liver damage and even convulsions and death. So it’s best to remove horses from a contaminated water source with algal blooms immediately. Algal growth is usually associated with large amounts of organic material in the water, often as a result of runoff from nearby fertilised fields.

Nitrate levels in natural or well water supplies are also a concern. Nitrate converts to the much more toxic nitrite in the rumen, which reacts with blood haemoglobin, reducing the availability of the blood to hold oxygen. Nitrites and ammonia should only be present in drinking water at very low levels. Ammonia may be present in supplies as a result of runoff from agricultural slurry, fertiliser or industrial waste. It rapidly oxidises to nitrite (which principally exists as an intermediate) and, in turn, to nitrate. Elevated levels of ammonia and nitrites are indicative of effluent contamination, and the source should be investigated and eliminated. For drinking purposes, removing nitrate is required and can be carried out by the installation of a reverse osmosis (RO) system.

When it comes to water safety, pesticides and herbicides are other worries. Though it can be expensive to test for these chemicals, it may be worth doing if you have significant concerns about the agricultural sprays being used in your area, or if you suspect solvents or other toxic chemicals have leached into your water from a nearby industrial facility. 

Until recently, the veterinary world had viewed iron toxicity in horses mainly as an acute condition and often only as a result of overdosing on iron supplements. However, research has shown that horses exposed to high iron levels in water, grass or hay over a prolonged period can accumulate the mineral in their livers, resulting in chronic iron overload. This iron overload can prevent the liver from carrying out its essential duties so vital to an exercising racehorse. High iron in water also can have a detrimental effect on the gut flora of horses, which can lead to all types of metabolic issues. Iron levels in well water vary greatly from region to region, and many hotspots have been identified over vast areas in different countries. Iron, like most minerals, can be filtered from water using filtration systems at the point of entry into the yard.

Once trainers have established a reliable clean source of water, they must then ensure that the distribution of clean water is maintained throughout the yard. That means placing covers on header tanks to prevent rodent or bird infiltration, cleaning water bowls, drinkers and buckets and finally flushing water lines to automatic drinkers on an annual basis. 

Then there’s the  question of which is better: watering using buckets or automatic drinkers? Both have positives and negatives. You can monitor the amount a horse drinks from buckets and then take buckets out of the box to clean as needed. The down side to bucketed water is that it’s labour intensive. Automatic drinkers are not labour intensive, but they do need to be checked daily to ensure they are working. They supply fresh water constantly, but you have no idea how much water a horse has drunk or not, and the systems need constant flushing and cleaning. 

Not all natural water sources are problematic, and not all artificially provided water is safe. Keeping a careful watch over the water your horses are drinking will allow you to detect contamination issues before they cause illness, dehydration or loss of performance.

Drinking water must be completely free from any microorganisms or contaminants which are considered a health risk.

The IEC provides water testing for equine, agricultural, domestic and commercial purposes. Water is tested for bacterial content including E. coli and total coliforms but also physical and equine-specific mineral profiles to an ISO 17025 standard. Water can pose a health risk for humans and animals when consumed, even though contamination may not be noticeable by taste, smell or even colour. 

Always read the label – experts guide us through equine healthcare products

By Lissa Oliver

We all want what’s best for our horse and we are happy to pay a price for the benefit of a happy, healthy and peak-performing horse. But what if that price is a hefty fine, suspension or even serious health consequences for us and our staff? How much trust can we afford to place in the claims of manufacturers, and do we pay enough attention to instructions? 

Ultimately, the responsibility for what goes into our horses lies fully with us. In this article, we’ll focus on the nutritional product labelling as well regulation of products which are promoted to consumers.

Nutrition

Dr Corinne Hills is an equine veterinarian with more than 20 years’ experience in practice in Canada, the Middle East, Europe, New Zealand and Australia, leading her to develop Pro-Dosa BOOST, manufactured from her own purpose-built, GMP-registered laboratory in New Zealand. 

Ingredient listings 

“We all want to make good choices and support our horses in the best way we can, with the best use of our finances,” Dr Hills agrees. “Horsemen always ask me about ingredients, but nobody ever asks about quality management. Similar products might appear to contain the same ingredients, but if the quality of the ingredients is poor, they will provide no benefit. Think about what you are spending your money on, and learn to read labels critically.

“It’s important to know the nutrient content of your feed and forage. In a perfect world everyone would consult their nutritionist and have forage tested, knowing exactly what their horse requires, what it is receiving and what supplements, if any, are needed. Horsemen don’t always feed a ready-prepared balanced feed. If they are mixing their own, they should be analysing the components of their feed. It’s easy and inexpensive, and your vet will know where you can send samples for analysis. Good feed companies provide the service for free. 

“Simply reading the label of feed and supplements could save you quite a bit of money. In my experience most people way over-supplement. A balanced feed manufactured by a reputable company should provide all of a horse’s requirements. Adding supplements could disturb the balance of the nutrients being fed. It is worth taking the time to understand nutrition to effectively support equine health. You can go to your feed company and ask their in-house nutritionist to suggest a tailored balanced diet that will suit most horses in your stable. If the feed company doesn’t have a nutritionist, it might be worth looking around for a new feed supply.

“Metabolism is quite complex, requiring a broad range of essential nutrients to function optimally. A lot of one nutrient doesn’t make up for deficiencies in another. The balance between nutrients is important. Some nutrients are required for the uptake and function of other nutrients. Too much or too little of one nutrient may result in deficiencies or toxicities of other nutrients. Imbalances can adversely affect health, performance and recovery. At a minimum, imbalances in a feed or supplement can render a product ineffective.

“For instance, vitamin C is required for the absorption of iron from the gut. Without vitamin C, iron passes straight through the gut and out in the faeces. Vitamin E, on the other hand, has a negative interaction with iron. It binds with iron and reduces its absorption, causing much of it to be wasted. So, in order for horses to use dietary iron effectively, it must be administered with vitamin C and without vitamin E. Iron balance is also closely related to zinc, manganese, cobalt, and copper.”

Nutrients Ratio

Ca:P 1-2:1

Zn:Mn 0.7-1.1

Zn:Cu 3-4:1

Fe:Cu 4:1

“B vitamins are known to work better when administered in optimal balance with each other. Amino acids are another good example of how nutrient balance is important. The balance of amino acids in a feed is as important as the amount of protein. Imbalances in amino acids limit the amount of protein in a feed that is usable in the horse to produce proteins and muscle cells, and the wasted amino acids that can’t be used for protein synthesis create a load on kidneys, elevate body temperature and elevate heart rates.

“It is also important to adhere to the instructions on the label. If insufficient doses are given, then no impact or a negative impact on the overall health of horses may result. 

“If you are buying a supplement that doesn’t contain what the label says, then at best, it’s a waste of money. At worst, it could be detrimental to your horses’ health. Giving too much of some nutrients is dangerous.”

Reading the label isn’t always an easy fix, however, as Dr Hills points out.

“Standing in a feed store, I couldn’t easily choose a good one as I couldn’t work out what was in each one by just looking at the labels. I had to photograph the labels and then put the information into a spreadsheet, convert all the quantities and units to a single standard, and then compare those contents to equine nutrient requirements. 

“How many horsemen do that? And if they don’t know what they are feeding their horses, aren’t they worried?”

Dr Hills has one simple tip. “If labels are easy to understand so that you can tell at a glance what you are giving your horse, then the manufacturer is probably proud of their formulation and believe it will stand up to scrutiny.

“If you have to perform too many calculations to figure out what you are giving, there is a fair chance that the formulation isn’t great. Some companies don’t actually want you to know how much or little of each nutrient is in their product. Take the time to do the maths and make sure you are making a true comparison before picking the cheapest or prettiest product on the shelf.

“When reading labels, it is important to consider all aspects of the nutrient composition—including balance, form and dose—in relation to the nutrient requirements of your horse.

“I found a huge number of products listing different combinations of nutrients that were included in different forms. For example, calcium could be provided as calcium carbonate, tricalcium phosphate, or calcium gluconate. They were also quantified with different units of measure, such as mg/kg, %, ppm, to name only a few. Then, they were to be given in different doses.

“The most confusing paste I found listed contents in terms of parts per million (ppm), percentages, and mg/kg. Then, the syringe was in pounds and the recommended dose in ounces.”

Quality control

“How do you know if a product is manufactured safely and meets label claims?” Dr Hills asks. “This information frequently isn’t on the label, but it’s just as important as the ingredients list; so it’s well worthwhile to make the effort to source the information. 

“You could look for a statement on the website about quality management, or you might have to ask the manufacturer some questions. Does the manufacturer have a quality management programme? GMP or ISO certification provides hard evidence of this.

“Be sure to ask every rep that visits your stable about quality management as they will almost certainly be the most readily available source for this information. Any rep that can’t talk competently about their company’s quality management programme probably represents a company that doesn’t have one.

“GMP stands for Good Manufacturing Practice, and this is a specific standard required for pharmaceutical producers. It is, however, voluntary for feed supplement manufacturers. A generic version of good manufacturing practice, abbreviated with small “gmp,” is a reference to a quality management system that is not government specified and inspected. It could be the same as GMP or it could be applied to a non-standardised or less complete quality system.

“If a company has either ISO or GMP certification, you can be sure that the supplements they produce will be safe, secure and generally meet label claims.

“Once you have selected a good quality, safe and healthy feed, then you can probably feed it to most of the horses at your stable. Spelling horses and smaller horses will need to eat less of it with more hay or grass. Racehorses or broodmares will need to eat more of it.”

Veterinary Medicines Directorate

The Veterinary Medicines Directorate (VMD) is the regulator of veterinary medicines in the UK. Louise Vodden and James Freer, from the Enforcement Department of the VMD, guide us through the draft documentation outlining the legislation behind the manufacture, sale and labelling of equine health and welfare products.

Guidance for advertising non-medicinal veterinary products

When advertising a non-medicinal veterinary product, it must not, by presentation or claims, suggest that it is medicinal. 

This applies to any advert—be it in magazines, online, at trade events or through client meetings and listing materials—that is aimed in part or in full at a UK audience. It is the responsibility of anyone engaged in marketing activities to comply with the VMD.

A veterinary medicinal product is legally defined as:

• Any substance or combination of substances presented as having properties for treating or preventing disease in animals.

• Any substance or combination of substances that may be used in, or administered to, animals with a view either to restoring, correcting or modifying physiological functions by exerting a pharmacological, immunological or metabolic action, or to making a medical diagnosis.

Medicinal by presentation

The first part of the definition above covers products that indicate they have a beneficial effect on an animal’s state of health. This is known as “medicinal by presentation”.

Prevention

This includes the destruction of parasitic infestations on an animal that may cause a medical condition, such as flea allergic dermatitis; hence, products that kill fleas on an animal are also classified as medicines.

Disease

This is considered to cover a broad range of conditions ranging from those caused by bacterial, viral or parasitic infections, to disorders resulting from various systemic dysfunctions, or deficiencies of substances essential for survival. We generally use the catch-all term “adverse health condition” for something wrong with an animal’s state of health. This includes injuries that pose a significant risk to wellbeing or would require more than the most superficial of management.

Medicinal by function

The second part of the definition covers two further aspects. The first relates to products containing substances with a recognised medicinal effect, commonly referred to as “medicinal by function”. The second covers the purpose of putting something in, or on, an animal to effect a change (restoring, correcting, modifying) in the way a bodily system works.

Restoring

This covers claims of restoration of function in any system within an animal that, for any reason, is not functioning within the normal range for an animal of good health. Even if there is no claim, be careful not to present before and after treatment expectations in your advert. For example, in one picture the dog can barely walk, and in another the same dog scampering along apparently healed. Such an advert would be considered medicinal by presentation.

Correcting

This covers any product used to address any deficiency or dysfunction in an animal’s systems. This includes issues like nutritional deficiencies in an animal, hormone imbalances, immunomodulation to address allergic reactions and correction of digestive dysfunction.

Modification

This includes any effect that changes the way an animal functions that is not covered by restoration or correction effects. In most cases, these tend to be enhancement claims such as “boosting”, “better”, “stronger”. Where such claims are made, the immediate question is, “better than what?” If the answer is, “better than normal,” then the product is considered medicinal by presentation. If the answer is, “better than an animal with condition X,” then it is considered as claiming to be medicinal by function.

Making medicinal claims

Non-medicinal products cannot claim to treat, prevent or control any adverse health condition. Nor can it refer, expressed or implied, to the treatment or prevention of a disease or adverse condition, or to improving the state of health of the animal treated.

For example, medicinal claims include a reference to the treatment or prevention of scours, colic, footrot, laminitis, sweet itch or pathological nervous conditions—or any other condition which is not the normal state of a healthy animal. This includes references to symptoms or any indication that the product is for use in an animal which is not in a normal healthy state.

References to the nutritional maintenance of a healthy animal, healthy digestive system or healthy respiratory system would not normally be regarded as medicinal claims. Though this does not extend to claims for preventing the occurrence of an adverse health condition or its symptoms.

Any implication that the product for use in an unhealthy animal and is intended for purpose of, or has the consequential outcome of, preventing a detrimental health state in an animal would predispose the product for a medicinal purpose for which it would require a marketing authorisation. Exceptions to this include particular nutritional purpose feeds, however, there are also specific restrictions on the claims these products can make.

Things to avoid in the advertising of non-medicinal products

• These products can only be presented for the maintenance of health in healthy animals.

The basic premise is that the purchaser of the product has a healthy animal and will be using it to support their animal’s state of health. Health maintenance does not include attempting to halt or slow the progression of a detrimental health state.

• Association with an adverse health condition

Narratives may not be used to suggest some terrible disease will or may happen, nor using statements like “4 out of 5 get” to present the product as the solution. This is considered a medicinal claim. Occasionally this approach is prefaced with the overtly medicinal company statement of intent that “we believe prevention is better than cure”.

Reference to specific diseases may be made in the form of a safety warning where use of the product may pose a risk, for example “WARNING: Not to be fed to horses with PPID”.

• Comparisons and presentation of equivalency to authorised medicines

A product not authorised as a veterinary medicine must never be presented, in any capacity, in comparison to any form of authorised medication. Marketing material for a non-medicinal product must not indicate or imply that the product can, or is intended to, be used as a substitute for authorised veterinary medicines. Nor should the use of a non-medicinal product be presented as resulting in the reduction of the use of any authorised medication. To do so is considered a medicinal claim for the product.

Disclaimers do not provide a remedy to the misrepresentation of a product in a medicinal capacity.

• Testimonials, quotes and endorsements

If customer testimonials are used in connection with the marketing of a product and report results containing medicinal claims, the claims will be regarded as those of the company marketing the product.

Claims made by a third party, such as magazine reviews or articles published by independent analysts, will be regarded as those of the company marketing the product where evidence confirms that the third party has a connection to the marketing company via solicitation, endorsement, sponsorship or funding.

If, for example, a vet who has been using a product for years expresses an opinion that is not being given in support of marketing a product, then it would just be an opinion. Any material published in support of marketing the product is considered to be marketing material. Whether that material is based on professional opinion, peer review studies, customer feedback, folkloric tradition or an “everybody knows”claim is not relevant. It must still adhere to the rules governing marketing material.

Herbal or “natural” products

Herbal products, “nutraceuticals”, or any products sourced in a way generally described as “natural” are treated like any other products. A natural origin provides no exemption from these requirements; they require authorisation if they are medicinal by function or presentation.

Biocides, insecticides and repellents

The following are always medicinal products requiring a marketing authorisation due to their use on animals:

• Veterinary product that contains substances that kill insects or external parasites (e.g., pyrethrins, pyrethroids or organophosphate compounds) as they are medicinal by function

• Veterinary product claiming to have, or which has, the function and  control of internal parasites

• Veterinary product claiming to treat or prevent a disease caused by a viral, bacterial or fungal infection

The following do not require an authorisation, provided they do not claim to treat or prevent disease:

• Product containing a repellent, such as diethyltoluamide or ethylhexanediol, provided it claims only to repel external insects

• Product applied only to housing or bedding

• Topical disinfectant applied to intact skin provided it does not claim to treat or prevent disease, including infection prevention (e.g., shampoos)

The marketing of these products is covered by legislation on biocides.

For further information regarding non-medicinal products, email enforcement@vmd.gov.uk or call +44 (0) 1932 338308 or +44 (0) 1932 338410

Probiotics – The key to a well-balanced equine gut

By Kerrie Kavanagh

It is no surprise that the health maintenance of the racehorse is a top priority for trainers. And probiotics can be used as a treatment modality to manipulate the gut microbiome to improve or maintain health. Equine studies to date have shown that probiotic strains can offer an advantageous approach to minimising disturbances in the gut microbial populations, repair these deficiencies—should they occur—and re-establish the protective role of the healthy gut microbiome. Other probiotic-associated health benefits include reducing diet-related diseases such as colic and laminitis, preventing diarrhoea, conferring host resistance to helminth infection, improving stress-related behavioural traits (e.g., locomotion) and even promote the development of an effective gut-brain communication pathway. 

Probiotics have been used by humans for more than 5,000 years with their development closely linked to that of dairy products and fermented foods. Today, probiotics are seen as an excellent non-pharmaceutical way to improve the health of both humans and animals, and there are a plethora of products to choose from. But what exactly is a probiotic, and how do they work? Why would your horse need one? What types of probiotics are available for horses? These are all questions that horse trainers ask frequently, which we will attempt to answer here. 

The Equine Gut Microbiome

Probiotics and the equine microbiome can benefit from a valuable symbiotic relationship; probiotics are seen as a restorative treatment modality for the gut, to re-establish the bacterial populations there and also to re-establish the protective role that the health gut microbiome confers to the host. But when we discuss the equine microbiome, what are we really talking about? 

The gut microbiota/microbiome can be categorised by anatomical location such as the oral microbiota/microbiome in the mouth and the intestinal microbiota/microbiome in the intestines, etc. Therefore, the gut microbiome pertains to the microbiota in the gastrointestinal tract. This population of microorganisms (bacteria, fungi, viruses, protozoa) is referred to as the ‘microbiota’ of the gut, while the term ‘gut microbiome’ refers to the genetic material associated with these microorganisms. The microbiome can be defined as the sum of the microbes and their genomic elements in a particular environment. If we look at the definition of the microbiome having the propensity to an equation, then any equation must be balanced; to maintain that balance is key. If the microbial community exists in an environment in a balanced state, then any upset or disturbance to the microbial populations will cause the balance to shift (known as dysbiosis). To maintain the balance, we need to firstly understand the way the microorganisms exist within their community (i.e. their microorganism-to-microorganism interactions and also microorganism-to-environment interactions) and secondly, their functioning role. If we can understand their (microorganism) position and role, then we can maintain the balance or re-establish the balance if a shift occurs.  

Fig. 1 Factors that can lead to gut Dysbiosis

The human intestinal microbiome is now recognised as an organ and likewise, the equine intestinal microbiome is deemed an ‘organ’ of the body and is vital for the breakdown of complex food and subsequent release of energy, protection against the pathogenic bacterial colonisation and in regulating the immune system and metabolic functions. There has been much debate regarding the content of the healthy equine microbiome, and even to deduce what ‘healthy’ or ‘normal’ is requires a level of understanding of the microbiota associated with healthy horses. This question has been posed by many researchers and frankly has yet to be answered with certainty. There are many reasons why the ‘normal’ microbiota keeps eluding us; and this can be attributed to the many reasons as to why the gut microbiota (of a healthy horse) can be affected (see Figure 1). It is thought that the diversity of the human gut microbiota and the general assembly of microbial communities within the gut (with the dominant phyla being classed as belonging to Firmicutes and Bacteroidetes) is a shared hypothesis across most species (i.e., humans and animals share a similar gut microbiome structure). Firmicutes and Bacteroidetes have been shown to constitute the main dominant phyla in equine, bovine, canine and feline gut microbiome studies indicating the cruciality of the role they play in the maintenance of a healthy microbial ecology in the gastrointestinal tract. Several studies do agree that dominant phyla of the equine gut microbiota are obligate anaerobes: the gram-positive Firmicutes and the gram-negative Bacteroidetes; other phyla are identified as Proteobacteria, Verrucomicrobia, Actinobacteria, Euryarchaeota, Fibrobacteres and Spirochaetes. Ninety-five percent of the  Firmicutes phyla contains the Clostridia genus in addition to genera related to gut health such as Lachnospiraceae, Faecalibacterium and Ruminococcaceae. The other main dominant phyla, Bacteroidetes, on the other hand contains a large variety of the genus. 

Role of the Equine Gut Microbiota

The role of the gut intestinal microbiota serves to protect and prevent disease. The gut microbiota has several purposes: prevention of pathogen colonisation by competing for nutrients, enrichment and maintenance of the intestinal barrier—their ability to renew gut epithelial cells and repair damage to the mucosal barrier, the breakdown of food and releasing energy and nutrients, such as synthesising vitamins D and K and also conserving and restoration of the immune system by the formation of antimicrobial metabolites and blocking access to the binding sites of the mucosal wall. The gut microbiota is also thought to play some role of influencing the neuro-active pathways that affect behaviour. It is not surprising to see that gut disorders and gastrointestinal diseases can arise when gut dysbiosis occurs. The role of the gut microbiota may have even more importance than is realised and may have a role to play with developing illness or disease later in life.

The microbial colonisation of the intestinal tract begins at birth. The foal begins its colonisation through contact with the microbiota of the mare’s vaginal and skin surfaces plus the surrounding environments to which the foal is exposed and reaches a relatively stable population by approximately 60 days in age. It is perhaps a fight for dominance to achieve establishment in the gut among the bacterial populations that sees the foal’s microbiota as being more diverse and quick to change when compared to that of the older horse. The subsequent colonisation of the intestinal tract will reflect the foal’s diet, changing environment, introduction to other animals, ageing and health.

What exactly is a probiotic?

Beneficial bacteria can be isolated and harvested to prepare a bespoke probiotc

The word ‘probiotic’ is of Greek origin meaning ‘for life’ and the WHO/FAO have defined probiotics as ‘live microorganisms which when administered in adequate amounts confer a health benefit on the host’.  People have long believed that exposure to non-pathogenic microorganisms can benefit the health of humans and animals. The thinking behind this is that daily consumption of sufficient numbers of ‘good’ microorganisms (either bacteria or fungi) can maintain a healthy population of microorganisms in the gut and benefit overall health.  

Probiotics are used to manipulate the bacterial populations of the gut in order to re-establish the delicate microbial balance there which, in turn, confers health benefits on the host. As the benefits associated with some of the ‘good’ bacteria within the gut became known, these were referred to as probiotic bacteria. 

How do probiotics work?

There are 4 main mechanisms by which probiotics are thought to exert their effects.

1. By inhibiting pathogen colonisation in the gut through the production of antimicrobial metabolites or by competitive exclusion; in other words, they prevent the ‘bad’ bacteria from growing in the gut.

2. By protecting or re-stabilising the commensal gut microbiota, probiotics can be a means to re-establish the balance of the gut microbial populations.

3. By protecting the intestinal epithelial barrier, they maintain the health of the intestinal wall.

4. By inducing an immune response, probiotics can boost the immune response and help prevent disease.

If we consider the definition of a probiotic as ‘live non-pathogenic microorganisms that, when administered in adequate amounts, confer a health benefit on the host’, then this reference to ‘adequate amounts’ must be emphasised, and the dose administered is critical to ensure that the probiotic has the desired effect. For horses, we must consider the route through the digestive tract that the probiotic strains must travel to arrive at their destination is a distance over 15 metres long. It is a race for survival! The gastrointestinal system has many obstacles along the passage such as the acidic stomach environment and the dangers of exposure to bile and digestive enzymes, in which they must survive. The initial dose of ‘live’ probiotic strains is therefore crucial to ensure survival in the gut. Prebiotics are ingredients such as carbohydrates and fibre, which promote the growth of these probiotic bacterial/yeast strains in the gut. Prebiotics are essentially the food for the probiotic strains and can help form a symbiotic relationship with the probiotic to improve the overall health status of the horse. 

Why would you need to give your horse a probiotic?

Gut dysbiosis is a fluctuation or disturbance in the population of microorganisms of the gut, which may be linked to a wide range of diseases in horses. Gut dysbiosis can be caused by many factors ranging from dietary changes, antibiotics, disease, intense exercise and training, age, worms, environment, travel, or even minor stress events—resulting in major consequences such as colic. Dysbiosis is generally associated with a reduction in microbial species diversity. 

Diet is one of the major factors contributing to gut dysbiosis. Unlike the ruminant cattle and sheep that use foregut fermentation, horses are hindgut fermenters. The large intestine is the main area where fermentation occurs. The horse utilises the microbial enzymes of the hindgut microbial population in the colon and caecum to break down the plant fibres (cellulose fermentation) sourced mainly from grasses and hay. The horse itself does not possess the hydrolytic enzymes that are required to break the bonds of the complex structures of the plant carbohydrates (in the form of celluloses, hemicelluloses, pectins) and starch; so therefore, it strongly relies on the microbiota present to provide those critical enzymes required for digestion. The main phyla Firmicutes and Bacteroidetes possess enzymes capable of breaking down the complex carbohydrates (such as starch and cellulose). Research has shown that forage-based diets (grasses and hay) promote the most stable gut microbiomes, but ultimately the equine athlete requires far more energy than a forage-based diet can supply. Supplementing the diet with concentrates containing starch such as grain, corn, barley and oats can affect the number and type of bacteria in the gut. Optimising diet composition is so important as carbohydrate overload—as seen with high-starch diets (>1g/kg body weight per meal)—can change the populations of bacteria in the gut, alter pH, upset digestion and the gut environment, and ultimately result in diseases such as colitis, colic and laminitis. The correct diet is essential for maintaining the delicate balance of bacterial populations. Probiotics can be used to either replace the bacteria missing in the gut and/or can help maintain the delicate microbial balance even in the face of adversity such as abrupt dietary changes, antibiotic treatment and stress.

What types of probiotics are available for horses?

There are several probiotic products on the market, and most are in powder or liquid form. There are two main categories of probiotics: generic and autogenous. Generic probiotics are off-the-shelf products that contain specific strains of bacterial or yeast, singularly or in combination. The Lactobacillus and Bifidobacterium families, Enterococci and yeasts such as Saccharomyces cerevisae and boulardii are the most common equine probiotic strains. Advantages of generic probiotics are that they are widely available, easy to administer, and they may be beneficial to horse health (if the strains are alive in sufficient numbers). Autogenous probiotics are specifically formulated using bacteria obtained from the horse’s own faecal sample and, as such, are uniquely adapted to that individual animal. These host-adapted bacteria are more likely to survive in the gut than non-adapted generic strains and can quickly replenish absent or low levels of bacteria unique to the individual horse, thus maintaining health.

Racehorse Bone Health: From a Nutritional Perspective

By Louise Jones

Strong, healthy bones are the foundation for racehorse soundness, but unfortunately skeletal injuries are an issue that every trainer will face. There are many factors involved in the production of strong bones; however, two key factors that we can influence are training and nutrition. 

Every trainer knows how important exercise is to ‘condition’ the bones, and we are constantly striving to improve training programmes so that sufficient strain is applied to signal an increase in bone development, whilst not straining the bones to the point of fracture; this is a difficult balancing. Perhaps more fundamental to this is the role of diet in supporting bone density, strength and repair.  Even minor nutrient deficiencies or imbalances can mean that the horse doesn’t receive the nutrients it requires for healthy bones and thus increases the risk of potential problems down the track.

Understanding how bone is formed and adapts in response to training, alongside the critical role optimal nutrition plays in these processes, can help to ensure skeletal soundness and minimise the risk of bone-related injuries.

Bone formation & remodelling

Bone formation occurs by a process of endochondral ossification; this is where soft cartilage cells are transformed into hard bone cells. Bone consists of three types of cells and an extracellular matrix. This extracellular matrix is made mainly from the protein collagen, which makes up to 30% of mature bone and is a key element in connective tissue and cartilage. The three types of cells in bone are:

• Osteoblasts: These are the cells that lay down the extracellular matrix and are responsible for the growth and mineralisation/hardening of bone.

• Osteoclasts: These cells are involved in the breakdown of bone, so that it can be replaced by new stronger bone. 

• Osteocytes: These cells work to maintain and strengthen when a bone requires modelling or remodelling.

Bone mineral content (BMC) is a measure of the amount of mineral in bone and is an accurate way of measuring the strength of a bone. Interestingly, about 70% of bone strength is due to its mineral content; calcium being the most notable and accounting for 35% of bone structure. A horse’s bones do not fully mature until they are about 5-6 years old. So, whilst a horse will have reached 94% of their mature height when they are a yearling, they will have only reached 76% of their total BMC. 

Although it may seem like mature bone is inert, it is in fact a highly dynamic tissue, and BMC is constantly adapting in response to exercise and rest by a process called remodelling.zBone remodelling is a complex process involving several hormones and nutrients. Essentially when mature bone ages or is placed under stress, such as exercise, small amounts of damage occur. This results in the osteoclast cells removing the old or damaged bone tissue. In turn, this triggers osteoblasts and osteocytes to repair the bone by laying down collagen and minerals over the area, thus strengthening the bones. It’s estimated that 5% of the horse’s total bone mass is replaced (remodelled) each year. It should be noted that during the remodelling process, bone is in a weakened state. Therefore, if during this period, the load applied to the bones exceeds the rate at which they can adapt, injuries such as sore shins can occur.

Bone strength & exercise

When galloping, a horse places up to three times its body weight in force on the lower limbs. The more load or pressure put on a bone, the greater the bone remodelling that will need to take place. Ultimately, this will result in new, stronger bones being formed. 

Studies have shown that correct exercise can increase bone density in the cannon bone, the knee and sesamoid bones; and this can help reduce the likelihood of skeletal injury. However, the intensity of training is key; low intensity exercise (trotting), whilst essential for muscle development, has been shown to only result in small change in cannon bone density. Whereas training at high speeds for a short amount of time (sprinting), rather than repetitive slow galloping, has shown to result in a significant increase in bone density. This is highlighted in a study using a treadmill where short periods of galloping at speeds over 27mph (43 km/hour) were associated with a 4-5% increase in the density of the cannon bone.

Whilst exercise clearly plays a pivotal role in bone density, doing too much too soon can be disastrous and result in issues such as:

• Sore/buck shins: This is a common injury in young racehorses. It is caused by excessive pressure on the bones resulting in tiny fractures on the cannon bone, which may not have fully mineralised (strengthened and hardened). This results in the periosteum (a fibrous membrane of connective tissue covering the cannon bone) becoming inflamed. 

• Bone chips: Another common skeletal injury in racehorses, mostly seen in joints, particularly in the knee. This is when a tiny fracture occurs in the joint, weakening the bone and ultimately resulting in a ‘chip’ of the bone becoming separated. 

When trying to maximise skeletal strength, periods of lower intensity exercise or rest are just as important as gallop work, as they give the bone a chance to remodel. However, prolonged rest will have a negative effect on skeletal health.  Research has looked at the loss of BMC in the cannon bone when horses were placed on box-rest (with 30 minutes on the walker) and found overall BMC was reduced. Therefore, even horses returning to work after a short period of 1-2 weeks of box-rest could potentially have a significant decline in bone density and thus be at increased risk of skeletal injury once exercise recommences. 

It’s also important to bear in mind that when a young horse starts training, it is normally coming from a 12–24-hour turnout. This is where the horse has the ability to gallop and play. However, once training begins, they are typically stabled from long hours with short intervals of low intensity training. Consequently, bone demineralisation can occur. In addition, during this early stage of training, bone will undergo a significant degree of remodelling in response to exercise. Initially this process makes the bone more porous and fragile before it regains its strength. As a result, research has shown that horses can have reduced bone density during the first few months of training, with bones being at their weakest and the horse more prone to issues such as sore shins between day 45–75 of training. 

It should be noted that even when training is carried out slowly, conditions such as sore shins can still happen as bone remodelling occurs at different rates in every horse and is influenced by factors such as track surface and design. While there is some information on exercise and bone development from which to make inferences, a definitive answer as to the perfect amount of exercise to support optimal bone development has not yet been found.

Nutrition & bone health

Exercise is essential to bone health, but nutrition plays an equally important role. Bone is continuously being strengthened, repaired and replaced. And if we can aid bone remodelling with good nutrition, we can decrease the likelihood of skeletal injury. The essential nutrients for bone health are protein, minerals and vitamins, including calcium (Ca), phosphorus (P), zinc (Zn) copper (Cu), vitamins A, D and K. 

Protein: Collagen is a protein and forms the bony matrix on which minerals are deposited. Feeding sufficient high-quality protein, rich in essential amino acids such as lysine and methionine, is therefore a key factor in the development of strong healthy bones. When selecting an appropriate feed for horses in training, both the level and quality of the protein it provides should be carefully considered; not all protein is equal.  

Calcium & Phosphorus: It is well documented that these essential minerals are the foundation of strong and healthy bones, making up 70% of the BMC. The ratio of calcium and phosphorus in the diet is also very important for bone mineralisation. This is because imbalances in the Ca:P ratio can result in the removal of calcium from the skeleton and may lead to bone demineralisation. The minimum Ca:P ratio in the diet should be 1.5:1, with the ideal ratio being at least 2:1 for young horses. It is important to note that adding other feedstuffs such as chaffs or cereals to the horse’s feed can alter the Ca:P ratio in the overall diet. For example, adding oats, which are high in phosphorus, will reduce the calcium to phosphorus ratio and this may adversely affect calcium absorption. On the other hand, including some alfalfa, which is high in calcium, can help to increase the Ca:P ratio if required. 

Copper & Zinc: Copper is an important mineral for bone, joint and connective tissue development. Lysyl oxidase is an enzyme that requires copper. It is responsible for cross-linking of collagen, and therefore copper plays an important role in the formation of new bone which requires a collagen matrix. Similarly, zinc is integrally involved in cartilage turnover; and research has shown that horses supplemented with zinc, as part of a complete mineral package, have increased bone mineral density compared to horses fed an unsupplemented diet. Copper and zinc are frequently found to be low in forage and therefore must be provided in the form of a hard feed or supplement. 

Vitamins: A number of vitamins play essential roles in skeletal health. For example, vitamin A is involved in the development of osteoblasts—the cells responsible for laying down new bone—whilst vitamin D is needed for calcium absorption. More recent research has also shown that feeding vitamin K improves the production of osteocalcin, the hormone responsible for facilitating bone metabolism and mineralisation. Furthermore, research in two-year-old thoroughbreds suggests that feeding vitamin K may help increase bone mineral density and thus potentially be beneficial for decreasing the incidence of sore shins. Although standard feed manufactures include vitamin A and D in their feeds, a few also now include vitamin K.

Supplementation for bone health

Young horses in training, those recovering from injury or returning to work following a rest will benefit from additional nutritional support targeted at maintaining improving bone health. In these situations, supplementing with elevated levels of calcium and phosphorus will help improve bone health. Look for a supplement containing collagen, which is rich in type I and II collagen, proteoglycans and glycosaminoglycans—all of which aid the bone remodelling process and help to maintain bone health. Choosing a supplement that also contains chelated copper and zinc, as well as vitamins A and D, will also help support bone mineralisation. 

In summary, skeletal injuries have a huge adverse effect on the racing industry and are a common cause of lost training days. Undoubtedly, adapting our training regimes, modifying our gallops and improving our management practices will all help to reduce the risk of bone-related injuries. Equally, the role of nutrition in bone health should not be overlooked. A balanced diet, rich in nutrients, minerals and vitamins, can contribute significantly to bone density and strength. Proper nutrition is an essential parameter of skeletal health, participating in both the prevention and treatment of bone diseases.  To achieve a strong, sound skeleton, you must feed the bones.

The Importance of forage testing

Forage (hay/haylage) is an important source of nutrients for horses in training. However, the levels of minerals such as calcium, phosphorus and copper present can vary enormously and depend on factors such as the species of grass and the land on which it was grown. It is recommended that you regularly test the nutritional value of your forage. This will highlight any mineral excess/deficiencies and allow for the ratios of certain minerals such as calcium and phosphorus to be assessed. In most cases, any issues identified can be corrected through using an appropriate hard feed and/or supplement.

Gut Health - Aspects of bad behaviour and how to fix it

By Bill Vandergrift, PhD

When performance horses behave or react in ways that are less than desirable, we as trainers and handlers try to figure out what they are telling us.  Is there a physical problem causing discomfort, or is it anxiety based on a previous negative experience? Or, is the bad behaviour resulting from a poor training foundation leading the horse to take unfamiliar or uncomfortable situations into their own hands? This usually triggers the fright and flight reflex instead of relying on the handler for direction and stability.  

Often when the most common conditions that cause physical discomfort are ruled out, it may be tempting to assume that the bad behaviour is just in the horse’s head or that the horse is just an ill-tempered individual. In my experience, most unexplainable behaviour expressed by performance horses is rooted in the horse’s “other brain,” otherwise known as the digestive system. In this article, I will explain what causes poor digestive health, the link between digestive health and brain function, and what steps can be taken to prevent and/or reverse poor digestive health.

Digestive health

While most trainers are familiar with gastric ulcers, symptoms and common protocols utilised to heal and prevent them, there still remains a degree of confusion regarding other forms of digestive dysfunction that can have a significant effect on the horse’s performance and behaviour. In many cases, recurrent gastric ulcers are simply a symptom of more complex issues related to digestive health.  Trainers, veterinarians and nutritionists need to understand that no part of the horse’s digestive tract is a stand-alone component. From the mouth to the rectum, all parts of the digestive system are in constant communication with each other to coordinate motility, immune function, secretion of digestive juices and the production of hormones and chemical messengers. If this intricate system of communication is interrupted, the overall function of the digestive system becomes uncoupled, leading to dysfunction in one or more areas of the digestive tract.

For example, a primary cause of recurrent gastric ulcers that return quickly after successful treatment with a standard medication protocol is often inflammation of the small and/or large intestine. Until the intestinal inflammation is successfully controlled, the gastric ulcers will remain persistent due to the uncoupling of communication between the stomach and lower part of the digestive tract.

How do we define digestive health? Obviously, digestive health is a complex topic with many moving parts (figuratively and literally). The main parts of a healthy digestive system include, but are not limited to 1) the microbiome, 2) hormone and messenger production and activity, 3) health of epithelial tissues throughout the digestive system, 4) normal immune function of intestinal tissue and 5) proper function of the mucosa (smooth muscle of the digestive tract) to facilitate normal motility throughout the entire length of the digestive tract.

Microbiome is key

A healthy and diverse microbiome is at the centre of digestive health. We now recognise that reduced diversity of the microbiome can lead to digestive dysfunction such as colic and colitis, development of metabolic disorders such as insulin resistance, reduced performance and increased susceptibility to disease. Research efforts leading to greater understanding of the microbiome have recently been aided by developing more sophisticated techniques used to identify and measure its composition in horses, laboratory animals, pets, livestock and people. While these research efforts have illustrated how little we really understand the microbiome, there have been significant discoveries stemming from these efforts already.  For example, a specific bacteria (probiotic) is now being used clinically in people to reverse depression resulting from irritable bowel syndrome (IBS). Bifidobacterium longum NCC3001 reduces depression in IBS patients by directly affecting the activity of the vagus nerve which facilitates communication between the brain and the digestive tract. It should be noted that Bifidobacterium longum NCC3001 has been demonstrated to be more effective at reducing depression in IBS patients than antidepressant drugs commonly used in these same cases. While we do not commonly recognise clinical depression as a physiological condition in horses, the same mechanisms that affect the function of the vagus nerve and brain chemistry in IBS patients can affect a horse’s behaviour and reactivity due to intestinal dysfunction, resulting in a horse that bites, kicks, pins its ears or otherwise demonstrates hyper-reactivity for no apparent reason, especially if this behaviour is a recent development.

One case in particular I dealt with years ago that had underlying suggestions of depression in a horse, and underscores the importance of a diverse and healthy microbiome for performance horses, was a horse that had been recently started in training and was working with compliance on the track. The problem was this horse seemed to be unable to find the “speed gear.” The trainer had consulted with various veterinarians, physical therapists, chiropractors and others in an attempt to pinpoint the cause for this horse’s apparent inability to move out; and it was everyone’s opinion that this particular horse had the ability but he simply wasn’t displaying the desire. In other words, he was “just dull.”  After reviewing this horse’s case and diet, I had to concur with everyone else that there was no obvious explanation for the lack of vigor this horse displayed on the track even though his body condition, muscle development and hair coat were all excellent. Despite any outward signs of a microbiome problem other than the horse’s “dullness,” I recommended a protocol that included high doses of probiotics daily, and within 10 days, we had a different horse. The horse was no longer dull under saddle; and when asked to move out and find the next gear, he would readily comply; by making an adjustment to the microbiome, this horse’s career was saved.

There is always a change to the microbiome whenever there is a dysfunction of the digestive system, and there is always digestive dysfunction whenever there is a significant change to the microbiome. Which one occurs first or which one facilitates a change in the other may be dependent upon the nature of the dysfunction, but these two events will almost always occur together. Therefore, efforts to maintain a viable and diverse microbiome will reduce the chances of digestive dysfunction and increase the speed of recovery when digestive dysfunction occurs.

Leaky gut

Even though the physiological basis of leaky gut has been understood for some time, leaky gut has not been a condition recognised to affect behaviour, performance or health in horses until recently. Today, leaky gut is quickly becoming a recognised dysfunction of the digestive system that has a multitude of negative effects on the overall well-being of horses including allergies, insulin resistance, uncharacteristic behaviour, picky appetite and reduced performance. As illustrated in Figure 1, leaky gut refers to a breakdown of the structures, referred to as tight junctions that hold adjacent intestinal cells together.

When the small and large intestines are healthy, the tight junctions between individual intestinal cells remain closed, forming a barrier between the inside of the intestinal lumen and the inside of the horse’s body. This barrier normally serves as a very important function by preventing complex molecules such as undigested proteins and carbohydrates as well as pathogenic and non-pathogenic bacteria from “leaking” through the intestine and entering the horse’s blood stream. Also note in Figure 1 that as you move your focus from left to right in the diagram, not only do the tight junctions become open, but the intestinal cells become more and more inflamed, eventually leading to total breakdown of the intestinal cells themselves. At this point, you not only have leaky gut, but now the condition has progressed from a leak to a flood, so to speak. This illustrates that the severity of leaky gut can vary from mild to severe with increasing severity also being associated with increasing intestinal inflammation.

Figure 1. Basic Physiology of Leaky Gut

 Image Courtesy of Kemin Industries.

As the severity of leaky gut increases, the communication between the different components of the digestive system is disrupted, and the coordination between the different sections of the digestive tract becomes uncoupled. The production of hormones such as serotonin and dopamine is altered, which has a direct effect on digestive function and brain function concurrently. This is one of the most obvious reasons why intestinal inflammation causes a horse’s behaviour and temperament to change.  Inflammation of intestinal cells initiates a self-propagating process that stimulates additional inflammation of the intestine and initiates systemic inflammatory processes throughout the entire body.  The self-propagating nature of intestinal inflammation is the reason why horses don’t just simply recover from it without assistance. In fact, I have worked with individual horses that have suffered from leaky gut for years based on their case history. The longer leaky gut has existed, the longer it will take to reverse in most cases.

In addition to leaky gut causing changes in behaviour and performance, leaky gut can also alter immune function and metabolic status. There is growing evidence that the initial cause of insulin resistance in many horses is in fact leaky gut. Intestinal inflammation causes a marked change in glucose homeostasis, which in turn reduces insulin sensitivity. Unfortunately, it appears that once insulin resistance is established, it is near impossible to reverse completely even if the leaky gut condition that caused it in the first place is successfully reversed.  

Leaky gut is also a common trigger for allergies in horses. It is well known that the majority of the horse’s immune system is located in the intestine. When the intestine “leaks,” undigested proteins, bacteria and other immune-stimulating agents gain access to the bloodstream, thus putting the immune system on high alert. Many horses respond to this situation by presenting with multiple allergies, many of which are reactive enough to warrant immunotherapy (allergy shots). I often hear in these situations that “my horse is allergic to everything”; and in many instances, this would seem to be the case. Fortunately, by reversing leaky gut and removing these immune-stimulating agents from the horse’s body, many of these allergies simply disappear. Keep in mind that horses can in fact be truly allergic to certain feeds and environmental agents, and these allergies have nothing to do with digestive health. It is best to consult with an experienced veterinarian and nutritionist to distinguish between true allergies and those caused by an overactive immune system triggered by leaky gut.

As illustrated in Figure 2, leaky gut can be caused by many different “triggers.” In performance horses, the most common triggers for leaky gut are: 1) stress (physical and emotional), 2) intense exercise, 3) heat stress and 4) various medications. Of these, stress is the strongest trigger for leaky gut due to the fact that stress of any kind increases circulating levels of cortisol. Cortisol breaks down the tight junctions of the intestine, which in turn results in leaky gut.

Figure 2.  Possible Factors Causing Leaky Gut in Horses

Preventing and reversing leaky gut

Almost all performance horses will present with digestive dysfunction or leaky gut at some point in time in their career. The reason is simple: stress is the strongest trigger for leaky gut, and all performance horses experience stress to one degree or another. Unfortunately, there is no exclusive marker for leaky gut at the present time. Researchers are getting close to developing a reliable diagnostic test for leaky gut as this article is written, but in the meantime it is best to detect digestive dysfunction and leaky gut by evaluating changes and observing symptoms presented by the horse. A partial list of symptoms to look for includes: a) not performing to the previous level or level that is expected, b) change in personality (e.g., grouchy or “leave me alone” behaviour, c) resistance to leg aids especially on right side (right dorsal colon is often inflamed), d) backing ears or biting when being saddled especially when the cinch is tightened, e) dull, f) prefers to eat hay rather than grain, g) manure has a funny odor or consistency, h) low fecal pH (herd specific), i) constantly shifting weight from one hind leg to the other in the stall, j) tight and “sunk in” in flank area, k) tight in back and hamstrings, l) eating a lot of grain but not gaining weight, m) dull coat and/or skin disorders, n) poor hoof quality, o) multiple allergies, p) improves while on omeprazole but quickly reverts when taken off, q) recurrent or chronic diarrhea and r) irreconcilable behaviour. (Note: No two horses will present with all of these symptoms or the same symptoms, but this list provides a guide for the most common symptoms to evaluate.

Since stress is the strongest trigger for intestinal inflammation and leaky gut, steps should be taken to remove as much stress as possible. For example, paying attention to biosecurity measures, transporting at times and with methods that reduce stress, adjusting training schedules to avoid heat stress and overexertion are things that can be done to reduce stress. Keeping forage (hay and/or pasture) in front of horses 24/7 is critical. Controlling the amount of grain-based feed fed per day can help in many cases. As a guideline, if you are having to feed more than 7 kgs (or 15 lbs) of grain per day to maintain a horse’s condition and energy level, you should suspect digestive dysfunction as one of the reasons so much feed is required.

If you suspect your horse is presenting with leaky gut, how can you help reverse it? Begin by continuing to provide “good quality” forage 24/7 and utilise a high-fibre, high-fat, low-soluble carbohydrate feed in place of a grain-based feed.

Second, utilise nutritional tools that are now available to stimulate closure of the tight junctions. These include nutraceuticals such as butyric acid, glutamine, bioactive peptides (plasma or colostrum), specific probiotics such as Bacillus subtillus PB6 and carnitine. There are products available currently that provide one or more of these nutraceuticals in the proper dosage.

Third, support a diverse and healthy microbiome with the use of probiotics and prebiotics. When selecting probiotics, numbers matter! It is preferred that any probiotic strain be dosed at a minimum of 1 billion CFUs (colony forming units) per day. Be sure to understand that this is per strain and not cumulative for a mixture of different probiotic strains. I would rather administer 10 billion CFUs of a single probiotic strain than 5 billion CFUs of a product containing a mixture of seven different strains.  Additionally, for optimal effectiveness of any probiotic, it is imperative that it be dosed in combination with prebiotics such as yeast cultures, mannan-oligosaccharides, fructooligosaccharides, or inulin, for example. Prebiotics and probiotics work synergistically to alter the diversity and overall activity of the microbiome in a manner that provides far superior results compared to either one by itself.

Fourth, provide anti-inflammatory activity to the intestine with omega-3 fatty acids. Flaxseed, chia seed, hemp oil, and fish oil all contribute to reducing inflammation in the intestine. The omega-3 fatty acid EPA from fish oil is especially effective as an anti-inflammatory agent for the intestine. DISCLAIMER:  In cases of severe leaky gut and severe intestinal inflammation, omega-3s may exacerbate the inflammation rather than reduce it. This will be noted within just 2–3 days by the horse presenting with notable diarrhoea. Additionally, omega-3s and coconut products are contraindicated for horses presenting with severe or chronic diarrhoea, as this is usually a reliable symptom of severe leaky gut, which is often made worse by these dietary components.

Fifth, include nutraceuticals to improve production of intestinal hormones and provide additional protection for intestinal cells. Possible choices include liquorice, slippery elm, aloe, arginine, citrulline, theanine, tryptophan, or alpha lipoic acid. Consult with a reputable supplement company for suggestions on which products and dosage are appropriate for your horse.

Feeding from the sales ring to racecourse

Author - Cath Dunnett

Horseracing’s international sales rings can perhaps be regarded or compared with the professional show circuit. To achieve optimum interest and price, youngsters not only need to be genetically well endowed but must be appealing to the buyers eye. Youngsters need to be in good body condition, ideally fit but not fat with good muscle tone, sufficient topline and a gleaming healthy coat. However the overall ‘picture’ desirable for the sales ring may not be the most appropriate for full training and competitive racing, and so trainers may find themselves needing to resculpture horses in their early days of training.  

Yearling Prep

Yearlings are prepared (‘prepped’) intensively for the sales ring. Whilst most yearling prep regimes will incorporate some exercise, this tends to be mostly walking; and yearlings may lack the established and better developed musculature needed for racing. There is also a high reliance on feeding to deliver the ‘sales ring look’.

Prep regimes are often short lived and designed to increase weight and condition relatively quickly, and to produce gleaming coat condition and topline—the latter of which can therefore be based on deposition of adipose tissue or fat, rather than muscle development or hypertrophy.

A prep period typically involves feeding a large amount of high energy, starch-rich feed over a relatively short period of time, typically 6-8 weeks. Research tells us that this prep period is likely to be one of the high risk times for non-glandular gastric ulcers to develop. Large starch-rich feeds, confinement, increased periods of stress and restricted access to pasture or forage are all significant risk factors for gastric ulcers.

Some yearlings will inevitably arrive at the trainer or pre-trainers yard with pre-existing non glandular ulcers, which may require veterinary treatment, or at the very least a sympathetic high forage, low-starch and sugar-based ration for early training. It may be controversial to suggest, but a longer slower period of prep for sales would perhaps allow for a greater contribution from exercise to build muscle, combined with a less intense feeding regime. However, time and economics probably contain too much deviation from the existing model. 

Bone Density

Yearlings that move through from studs to sales prep and then into a training yard undergo a very big change in their feed and management that is worthy of consideration. A stud regime and diet are very different to both sales prep and pre-training, in terms of composition and environment. At stud, these young animals spend a large portion of their day at pasture, with a generally small amount of top up feed or balancers to complement the grazing.

A diet, which is typically high in pasture and forage and low in cereals, allows minerals such as calcium to be firmly sequestered in bone, maintaining bone density. In horses on good pasture, this is aided by the high vitamin K1 content of pasture, which is needed to activate osteocalcin involved in the sequestration of calcium in bone. In contrast, with a high-cereal, low-forage prep or pre-training diet—as a result of quite complicated homeostatic mechanisms involving hormones such as parathyroid hormone—calcium can become relatively more mobilised from bone. The characteristic drop in bone density commonly seen in racehorses in the first 60-90 days of training can be the physical result of this phenomenon.  

Forage First

Yearlings may come into training on the larger side of perfect for racing; and so it may, at first glance, seem counterintuitive to feed plenty of forage at this time. However, in early training it is a worthwhile exercise, as it establishes good eating habits.

Horses in training often self limit their forage intake, as training progresses and appetite is reduced, which can contribute to problems including inability to maintain condition, gastric ulcers and tying up if the forage intake drops too low. Better to start from a slightly higher intake early on, than to find a horse on a forage knife edge later in training.

Forage, whether hay or haylage, contributes significantly to energy and electrolyte intake and is a particularly rich source of potassium—an important electrolyte for overall metabolism and muscle function. Leguminous forage such as alfalfa/lucerne is highly digestible and so has a reduced effect on gut fill (hay belly). Alfalfa is equally rich in calcium to help buffer the natural mobilisation and loss of calcium from bone during early training.

A couple of kilograms of alfalfa per day complements a more traditional less digestible hay such as Timothy. The added advantage of feeding a decent amount of forage is that the level of concentrate feed needed will also be reduced. Forage provides energy mainly from fibre and so is not generally associated with excitability, with the energy provided being colloquially known as slow-release energy.

A decent amount of forage for a horse in training is about 1.5% of bodyweight; so for a 500kg horse, that’s about 7-8kg or 4 typical slices. For haylage, this needs to be slightly higher to account for its higher water content.

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Nutrition Analysis - Understanding equine feed labelling

By Dr Catherine Dunnett, BSc, PhD, R.Nutr

Understanding a bit about feed labelling and feed manufacturing is worth the drudge, as it can help you make better choices for your horses in training and maybe even save a few pounds or dollars. Whilst the information that a feed manufacturer must legally provide can vary from country to country, it is broadly similar. The purpose of feed labelling is primarily to give information about the feed to a potential customer, allowing informed choices to be made. However, it also provides a measure against which legislators and their gatekeepers can ensure feed manufacturing is consistent and that the feed is not being misrepresented or miss-sold.

The on-bag information is most often separated into what’s known as the statutory statement (or the legally required information) and then other useful information which features outside of the statutory statement. The statutory information can be found in a discrete section of the printed bag, or it could be located on a separate ticket, stitched into the bag closure. Whichever is the case, this is the information legally required by the country’s legislators and which the feed manufacturer is legally bound to adhere to.  Typically, the information required within the statutory statement includes for example:

• Name, address and contact details of the company responsible for marketing and sale of the feed.

• The purpose of the feed, for example for pre-training or racing.

• Reference to where the feed has been manufactured. Some companies do not have their own manufacturing facility and will use a contract manufacturer. In the UK, a feed mill manufacturing feed must be registered and on the UK list of approved feed business establishments and there is a number, colloquially known as a GB number, which refers to the feed mill’s registration. A useful snippet is that if this GB number changes on pack, this may mean that the manufacturer has switched to a different mill.  

• A list of ingredients in the feed in order of inclusion. The first ingredient will have the highest level of inclusion and the last being the least level.

• A declaration of analysis, which is used to describe the nutritional characteristics of the feed is quite limited in what can legally be declared. There is a predefined legally binding list of analytes that must be declared in this section, which depends on the type of feed. For example, this might include percentage protein, oil, crude fibre, ash, as well as the level of added additives such as copper, vitamins A, D and E, as well as any live microbiological ingredients, or preservatives, binders etc. In addition, the analysis must be carried out using specific laboratory methodologies set out in the legislation. Feed manufacturers are allowed some tolerance on analysis, or limits of variation around their declaration to account for variation in sampling and manufacturing as well as the analytical variation itself and this can be as high as 10-20% in some instances for example.   

• The level and source of additives. For example, added copper must be declared and the level (mg/kg) and source (copper sulphate or if as a chelate, copper chelate of amino acid hydrate) stated. 

• Any additives (i.e., ingredients that don’t contribute to the nutritional value of the feed) can only be used if they appear on an authorised list of additives—meaning they have passed scrutiny for safety and efficacy. This list of additives pre-Brexit was maintained by the EU and since Brexit, whilst we can theoretically modify on our own terms, the reality is that we have largely adopted the EU list.  

There is a lot of useful information that is not legally allowed within the statutory statement that you will often find on a separate section of the bag, or indeed on a company website. For example, other analyses such as percentage of starch and sugar are often useful when choosing an appropriate feed and an estimate of the level of digestible energy (DE MJ/kg) is also helpful. Feeding guides also generally appear outside the statutory statement and can be quite useful. Whilst I am a firm believer in looking at the horse to help set the required amount of feed, feeding guides do give vital information, particularly about the likely minimum amount of this feed required to deliver a suitable level of vitamins and minerals.  

When being first really counts…

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Why are gastric ulcers still a significant concern for horses in training?

By Catherine Rudenko

With the advances in scoping and increased awareness of gastric ulcers, along with the high prevalence found in horses in training, one may wonder, Why is this condition still such a problem? Do we not know enough to prevent this condition from recurring?

The short answer is that much is known, and for certain, there are effective medications and many feeds and supplements designed to manage the condition. The underlying problem is that the factors leading to ulceration, at least the most significant ones, are fundamental to the routine and management of a horse in training. Quite simply, the environment and exercise required are conducive to development of ulcers. Horses in training will always be at risk from this condition, and it is important to manage our expectation of how much influence we can have on ulcers developing, and our ability to prevent recurrence.

Clarifying Gastric Ulceration

Before considering how and why ulcers are a recurrent problem, it is helpful to understand the different types of gastric ulceration as the term most commonly used, Equine Gastric Ulcer Syndrome (EGUS), is an umbrella term which represents two distinct conditions.

The term EGUS came into use in 1999 and represented ulceration of the two separate locations in the stomach where ulcers are found: the squamous and glandular regions. The two regions are functionally different, and ulceration in either location has different causative factors. This is important when considering what can be managed from a risk point of view at a racing yard. The term EGUS is now split into two categories: Equine Squamous Gastric Disease (ESGD) and Equine Glandular Gastric Disease (EGGD).

ESGD is the most commonly occurring form and the focus of dietary and management interventions. The majority of horses in training have the primary form of ESGD where the stomach functions normally. There is a secondary form that relates to a physical abnormality which causes delayed emptying of the stomach.

The condition ESGD is influenced by the training environment and time spent in training as noted by researchers looking at prevalence of horses out of training compared to those within training. In this case, 37% of untrained thoroughbred racehorses had ESGD and this progressed to 80-100% of horses within two to three months of training. This effect is not unique to thoroughbreds and is seen in other breeds with an ‘active workload’; for example, standardbreds progress from an average of 44% ESGD in the population to 87% when in training. Such research is helpful in understanding two things: firstly, that ulcers in the squamous section can occur outside of training, and that the influence of exercise and dietary changes have a significant effect regardless of breed. Even horses in the leisure category, which are thought of as low risk or at almost no risk at all, can return surprising results in terms of prevalence.

Risk Factors

There are multiple risk factors associated with development of ESGD, some of which are better evidenced than others, and some of which are more influential. These include:

• Pasture turnout

• Having a diet high in fibre/provision of ‘free choice’ fibre

• Choice of alfalfa over other forages

• Provision of straw as the only forage source

• Restricted access to water

• Exceeding 2g of starch per kilogram of body weight

• Greater than 6 hours between meals (forage/feed)

• Frequency and intensity of exercise

• Duration of time spent in a stabled environment combined with exercise

Of these factors, the stabled environment—which influences feeding behaviour—and exercise are the most significant factors. The influence of diet in the unexercised horse can be significant, however once removed from pasture, and a training program is entered into, ulceration will occur as these factors are more dominant. An Australian study of horses in training noted the effect of time spent in training, with an increase in risk factor of 1.7 fold for every week spent in training.

Once in training, there is some debate as to whether provision of pasture, either alone or in company, has a significant effect. …

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Nutrition - antioxidants - their role in racing - is there merit in specifically supplementing antioxidants to enhance performance?

By Catherine Rudenko

Antioxidants are substances that slow down damage to organisms created by the presence of oxygen. The need for antioxidants is always there, in all species, increasing as exercise intensity and duration increase. Is there merit in specifically supplementing antioxidants to enhance performance?

The nature of antioxidants

There are many forms of antioxidants naturally present within the body and supplied through the diet. One key feature of antioxidants is that they are ‘team players’. No one antioxidant alone can maintain the system, and some will only function in the presence of another antioxidant.

The role of an antioxidant is to keep reactive oxygen species (ROS) or free-radicals created in the presence of oxygen at an optimum level. Oxygen is required for life, it is always present, but as an element, it is highly reactive and so can also have an adverse effect on the body. The reactivity of oxygen in the body produces ROS which cause damage to cellular components such as DNA, proteins and lipids of cell membranes. Some ROS also have useful cellular functions, and so the purpose of antioxidants is not to eliminate ROS altogether but to maintain a healthy balance. In general, antioxidants operate in two ways: either preventing the formation of an ROS or removing it before it can cause damage to a cell component.

Sources of antioxidants

There are multiple sources of antioxidants including vitamins, enzymes and nutrient derivatives. Other nutrients such as minerals, whilst not having antioxidant properties, are also involved as their presence is required for the functioning of antioxidant enzymes. Two key examples are zinc and selenium.

As with many body systems, the ideal healthy balance can often go awry. When the level of ROS present overwhelms the capacity of antioxidants present, the body experiences oxidative stress. There are three main reasons for a horse in training experiencing oxidative stress:

• Increased exposure to oxidants from the environment

• An imbalance or shortage in supply of antioxidants

• Increased production of ROS within the body from increased oxygen metabolism during exercise

Oxidative stress is of concern as it can exaggerate inflammatory response and may be detrimental to the normal healing of affected tissues. Oxidative stress during strenuous exercise, such as galloping or endurance, is typically associated with muscle membrane leakage and microtrauma to the muscle. Oxidative stress is now understood to play a role in previously unexplained poor performance.

Dietary antioxidants photo: horse eating?

Given the demands of training and the regularity of intense exercise and racing itself, the use of dietary antioxidants is an important consideration. As antioxidants are generally best considered as a cocktail, it is necessary to give consideration to provision of nutrients and their derivatives across the total daily diet.

The majority of racing feeds will be formulated to provide a good cocktail of basic antioxidants or their supporting minerals. All feeds will contain vitamin E, selenium and zinc for example. Some, but not all, feeds will also provide vitamin C. The source of these nutrients may also differ; for example, some feeds will contain chelated zinc or organic selenium, which offer improved availability. The source of vitamin E will also vary—the majority being provided as synthetic vitamin E; but some will include natural sources of vitamin E, which is more effective.

TOP: Oxidative stress is now understood to play a role in previously unexplained poor performance.

Once a good base diet is in place, consideration for strategic use of individual antioxidants may then be warranted to further enhance the capacity of the body to mitigate the effects of ROS on the muscle. Three popular and commonly used antioxidants are vitamin E, vitamin C and more recently coenzyme Q10.

Vitamin E

As a lipid-soluble antioxidant, vitamin E provides defence against ROS in cells, playing an important role in maintaining integrity of cell membranes. Vitamin E is the most commonly supplemented antioxidant. There are established recommended daily intakes for vitamin E, typically 1000 IU per day for a horse in training; however, further supplementation beyond the basic nutritional requirement can yield benefits. Modern race horse feeds are well fortified—the majority providing upwards of 300 IU/kg, resulting in an average daily intake of over 2000 IU/day.

Intakes of above the base rate have been investigated for their effect on CK (creatine kinase) and AST (aspartate aminotransferase)—two markers of muscle damage. One such study used endurance horses whereby intakes ranged from 1150 IU up to 4750 IU per day. Elevated intakes of vitamin E correlated with lower levels of CK and AST suggest that vitamin E can affect muscle membrane permeability and injury to muscle during exercise.

As a guide to improving antioxidant capacity, an intake of up to 5000 IU per day would be appropriate for a horse in training. Vitamin E intake is influenced by the level of fats fed in the diet; and where additional oils are added, further vitamin intake E is required, as vitamin E will be utilised in stabilising the oil itself. Fats fed in a dry format, such as extruded rice bran, are normally fortified with vitamin E for this reason and do not require further supplementation.

Vitamin E is available in feeds and supplements in two forms: synthetic or natural. The natural form, d-alpha-tocopherol, is made up of a single isomer (chemical unit). The synthetic form, dl-alpha-tocopherol, is made up of eight different isomers—only one of which is molecularly the equivalent of natural vitamin E. The dose rate required to increase serum vitamin E levels in horses is lower for natural E than synthetic vitamin E.

The increased bioavailability of natural vitamin E has led to further research in comparing this source against synthetic vitamin E for efficacy against oxidative stress and physical gait changes. The study used 3 diets: a control diet with the standard recommended intake of 1000 IU/day provided by synthetic vitamin E; a higher intake synthetic vitamin E diet of 4000 IU/day; and a high intake of natural vitamin E at 4000 IU/day. The study lasted for six weeks and measured serum levels of vitamin E at various time points along with markers of oxidative stress, CK and AST levels, and gait analysis.

The key findings:

All diets increased serum vitamin E over time; however, the increase was not significant in the diet, providing only 1000 IU/day of synthetic vitamin E. The greatest difference in serum vitamin E was seen in the natural vitamin E diet where levels increased by 77.25% from day one to the last time point.

Oxidative stress was measured through multiple tests including oxidation of lipids (TBARS). Horses supplemented with natural E had lower levels of lipid oxidation markers than both synthetically supplemented horses at the second exercise test, which occurred after six weeks of fitness training.

AST levels were lower within the two hours post exercise of natural E supplemented horses compared to synthetic vitamin E horses; however, by 24 hours, the difference was no longer significant. There was no noted significant effect on CK.

Gait analysis before and after exercise showed better movement of horses that were supplemented with natural vitamin E. These horses experienced less of a reduction in their stride duration post exercise, potentially indicating less muscle soreness due to less oxidative stress.

As vitamin E is well proven to be an effective antioxidant, it may be tempting to think that ‘more is better’; however, as with all nutrients, there is a safety limit to consider. Current research indicates that supplementing at 10 times the base level—an intake of 10,000 IU/day—may result in poor bone mineralisation and impair beta-carotene (vitamin A) absorption. An intake of 4000-5000 IU/day based on the research above and other studies would appear effective whilst also being well below the presumed safety limit.

Vitamin C

Ordinarily horses can manufacture adequate vitamin C within the body, unlike humans that require direct supplementation. Additional vitamin C is required and often recommended when the body is challenged through disease or periods of stress. …

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Can nutrition influence EIPH? -Catherine Rudenko investigates alternative and supportive therapies as trainers seek to find other means of reducing the risk or severity of EIPH

By Catherine Rudenko

EIPH (exercise-induced pulmonary haemorrhage) was first identified in racehorses in the 16th century. Since this time, the focus has been on mitigating the haemorrhage. Management of EIPH largely revolves around the use of furosemide, dependent of jurisdiction, may or may not be used on the day of racing. Alternative and supportive therapies are becoming increasingly popular as trainers seek to find other means of reducing the risk or severity of EIPH.

Nutrition and plant-based approaches are part of an alternative management program. Whilst research is somewhat limited, the studies available are promising, and no doubt more work will be done as using furosemide becomes more restricted. There are several directions in which nutrition can influence risk for EIPH, including inflammatory response, blood coagulation, cell membrane structure, hypotension and reducing known lung irritants.

Exercise- induced injury may exacerbate the severity of EIPH as a result of the delayed sealing of damaged micro vessels.

The various approaches are all supportive, working on altering an element of risk associated with the condition. Some are more direct than others, focusing on the effect on red blood cells, whilst others work on some of the broader lung health issues such as reducing mucus or environmental irritants. 

None are competitive with each other, and there may be an advantage to a ‘cocktail’ approach where more than one mode of action is employed. This is a common practice with herbal-based supplements where the interactive effects between herbs are known to improve efficacy. 

Cell membrane

The red blood cell membrane—the semipermeable layer surrounding the cell—is made up of lipids and proteins. The makeup of this membrane, particularly the lipid fraction, appears to be modifiable in response to dietary fatty acids. Researchers feeding 50mls of fish oil found a significant increase in the percentage of omega-3’s in the cell membrane.

Essential fatty acids (EFA’s), omega 3 and omega 6, are important cell membrane components and determine cellular membrane fluidity. Fluidity of a cell membrane is important, particularly when pressure increases, as a cell membrane lacking in fluidity is more likely to break. A cell that can deform, effectively changing rather than breaking, has an advantage and is linked with improved exercise performance in human studies. Inclusion of fish oil in the diet increases the ability of red blood cells to deform.

Kansas State University investigated the effect of omega supplementation on 10 thoroughbreds over a five-month period. The diet was supplemented with either EPA and DHA combined, or DHA on its own. EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid) are specific forms of omega-3 fatty acids commonly found in oily fish. When supplementing the diet with both EPA and DHA, a reduction in EIPH was seen at 83 days and again at 145 days. Feeding DHA on its own did not produce an effect.

Fish oil contains both EPA and DHA and is readily available, although the smell can be off-putting to both horse and human. There are flavoured fish oils specifically designed for use in horses that overcome the aroma challenge and have good palatability. 

Inflammatory response and oxidative stress

Airway inflammation and the management of this inflammatory process is believed to be another pathway in which EIPH can be reduced. Omega-3 fatty acids are well evidenced for their effect in regulation of inflammation, and this mode of action along with effect on cell membrane fluidity is likely part of the positive result found by Kansas State University. 

Kentucky Equine Research has investigated the effect of a specific fish oil on inflammatory response with horses in training. The study supplemented test horses with 60mls per day and found a significant effect on level of inflammation and GGT (serum gamma-glutamyl transferase). GGT is an enzyme that breaks down glutathione, an important antioxidant. As GGT rises, less glutathione is available to neutralise damaging free radicals, creating an environment for oxidative stress.

Kentucky Equine research results

A horse’s red blood cells are more susceptible to oxidative stress than humans, and maintaining a healthy antioxidant status is important for function and maintenance of cell integrity.

Rosehip

Supplements for bleeders will often contain relatively high doses of antioxidants such as vitamin C and vitamin E to support antioxidant status in the horse and reduce risk of damage to cell membranes. Vitamin C has also been shown to benefit horses with recurrent airway obstruction and increase antibody response. Dose rates required for an effect range from 15-20g per day. If including high doses of vitamin C in the diet, it is important to note that any sudden withdrawal can have negative effects. Gradual withdrawal is needed to allow the body’s own mechanisms for vitamin C production to recognise and respond to the change in status.

Rosehips are natural potent antioxidants containing many active substances. Research into the effect of rosehips specifically on red blood cells has shown they have a high efficacy when assessing their ability to ameliorate cell damage.

Hypotensive herbs

Caucus carota – wild carrott

The essential oil of caucus carota species is a well-documented oil having a hypotensive, lowering of blood pressure effect along with antifungal properties. Its antifungal effects are noted against aspergillus species, a common cause of poor respiratory health. Allium sativum is also well known for its ability to lower blood pressure. An initial study (data unpublished) into the effects of these two plants along with herbs reported to alleviate mucus in the lungs has shown promising results in a group of horses in training. 

Prolonged blood coagulation

As prolonged blood coagulation is cited as a possible factor for EIPH, herbal products that are noted for their ability to enhance coagulation are in certain parts of the world widely used as part of managing EIPH. …

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