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

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 behavior, something that can easily be overlooked when the ‘what is fed’ is the same for all horses in the barn. Individual behavior 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 stable. 

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 behavior happens during daylight hours, typically 60-70% of time available (3).

During nighttime hours the amount of time spent as feeding behaviors 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 above 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 4:45 am until 9:15 pm.  

One of the key aspects of natural feeding behavior 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 behavior 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 4.85lbs / 2.2kg of a cubed racing feed alongside 1.3lbs / 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 behavior 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 behavior. 

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 fiber 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 fiber-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, stabilizing 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 maximize 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 nutrition for health, performance and 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  fiber 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, fiber 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, fiber 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, diarrhea, colic or colitis), muscle dysfunction (eg: rhabdomyolysis (known as ‘tying up’), defective bone mineralization (expressed as increased incidence of stress fractures and developmental orthopedic 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 fiber 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 fiber (relative to other grains) are oats.

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 recognized 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 fiber 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 estrogen. Lignans are linked to a reduced risk of developing osteoporosis, heart disease and cancer.

Fiber - Flaxseed contains both the soluble and insoluble types of fiber 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 behavior 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 compromized 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 fiber. 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 life span. 

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

Nutrition - supporting the recovery process to improve performance - Train, Race, Recover, Repeat

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 fiber rich plant material.

Fiber is important to the horse for several reasons. The digestion of fiber releases energy and other key nutrients to the horse. Fiber also acts to provide bulk in the digestive tract, thus helping maintain the passage of fecal material through the system. Fiber 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, behavioral 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 maximize performance. A great deal of research and expertise are utilized by the major feed companies to ensure that modern racehorse concentrate feeds provide adequate provision of the major nutrients required and minimize 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 liters), 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 behavior. 

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 neutralized. 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 present 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 minimize 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 behavioral 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 neutralize 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 liters 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 fibers 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 optimize levels for the following day’s travel or race. The benefit of providing electrolytes with feed is that it will minimize 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-recognized 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.

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 minimizing health issues and maximizing 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.

Pekacar, S. et al (2021). Anti-Inflammatory and Analgesic Effects of Rosehip in Inflammatory Musculoskeletal Disorders and Its Active Molecules. Curr Mol Pharmacol. 14(5), 731-745.

Rivero, J.-L.L. et al (2007). ‘Effects of intensity and duration of exercise on muscular responses to training of thoroughbred racehorses’. Journal of Applied Physiology 102(5), 1871–1882.

Siciliano, P.D. et al (1997). Effect of dietary vitamin E supplementation on the integrity of skeletal muscle in exercised horses. J Anim Sci.75(6), 1553-60.

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.

van den Berg, J. et al (1998). Water and electrolyte intake and output in conditioned Thoroughbred horses transported by road. Equine Vet J. 30(4), 316-23.

Vatistas, N.J. et al (1999) Cross-sectional study of gastric ulcers of the squamous mucosa in thoroughbred racehorses. Equine Vet J Suppl. 29, 34–39.

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.

How HISA has affected the marketing and selling of equine supplements - What trainers need to know

Article by Ken Snyder

In 1834, Thomas Day of Day & Sons in the UK. introduced Day’s Black Drink, an elixir for horses to relieve colic, chills, “low condition” and something called “gripes.” There is no record of the ingredients, and that is probably something best left unknown.

Black Drink was the first known supplement, or product made from natural, not synthetic, substances, as this was the early 19th century. So, too, is heroin derived from a natural substance—poppies. (Created from morphine in 1874, its use on the racetrack was prevalent enough in the early 20th century to help fix races that “horse” became slang for the narcotic in recent history.)

Supplements today range from useless and quackery to many that are considered effective in horse health care by many trainers on the racetrack. In fact, the majority of  Thoroughbred trainers utilize supplements with feed.

Like therapeutic medications and illegal substances, dietary supplements are under the purview of the Horse Integrity and Safety Authority (HISA). Like their drug counterparts, HISA is instituting uniform regulations for supplements in all 50 states. The task falls specifically to the organization’s Horse Integrity and Welfare Unit (HIWU).

Good, bad, or indifferent, the intent of this organization, inarguably, is noble: to make racing safer and healthier for the horses. 

Supplements, however, are seemingly lost in the fog in the scrutiny and attention paid to perhaps the biggest problem in horse racing: medications.

There are potential hazards with supplements, however, and uniform rules across all U.S. racing jurisdictions are in place just as with medications. The key regulation that is now applicable in every HISA jurisdiction specifies that “orally administered vitamins“ and “unsupplemented isotonic electrolyte solutions by oral or intravenous administration” may be administered up to 24 hours prior to post time. This may differ from prior state regulations.

Alexa Ravit, director of communications and outreach for HIWU, outlined the objectives of this regulation and all HISA “regs” in response to an email:

“HISA’s supplements-related regulations (and in particular addressing ‘drug claims’) are intended to protect horsemen from 1) fraudulent or unproven claims of effect; 2) the unknown safety risk to horses in administering these products; and 3) products where the risk of contaminants or unknown components is high due to lack of independent quality controls.”

The task of monitoring and regulating dietary supplements is not nearly as challenging as that for medications, but it is no slam-dunk either. Also, while medications and new withdrawal times for permitted drugs might be a trainer’s focus, trainers should know that, while supplements by and large are safe, there are things to watch for with their use. 

In simplest terms, managing supplements for trainers under HISA/HIWU is following three steps: (1) reading labels (more on this below); (2) being careful in using dietary supplements in combination with approved medications; and (3) not accepting free supplements without understanding what’s on the label.

Mislabeled supplements, according to Rivet, are the major thing that can get a trainer and owner in trouble. She wrote, “If…the product’s labeling…includes a health or structure/function claim, the product is a drug, not a dietary supplement.” Also, drugs are FDA-approved and will carry that information on the label. Supplements won’t. 

In short, trainers need to look first to make sure the supplement does not say “FDA approved.” Supplement labels also should not make “structure/function” claims. HIWU lists these examples:

− Decreases or prevents exercised-induced pulmonary hemorrhaging (EIPH)

− Prevents or treats gastric ulcers
− Manages pain caused by osteoarthritis
− Controls inflammatory airway disease 

− Increases cardiac output
− Increases red blood cell production

The claims are definite, positive and apparently proven by results, warranting approval by the FDA.

Contrast these claims against what will be found for dietary supplements: 

− Sustains lung health
− Maintains gastrointestinal health
− Supports heart health
− Supports bone strength
− Promotes healthy metabolism
− Replenishes electrolytes lost through exercise and sweating

Labels on dietary supplements sound good but stop short of making a promise and, in a couple of instances, are vague at best. “Sustains lung health” and “maintains gastrointestinal health” are things you would want a horse to have after lung or gut issues are solved, and maybe skate closest to a claim like a drug. What supports heart and bone health and strength, respectively, is anybody’s guess. The same goes for promotes healthy metabolism. (Maybe the label will tell one how.) Replenishes electrolytes is a straight-up promise that evidently is achieved with dietary supplements and not drugs. (Gatorade for humans comes to mind.) 

To make another simple distinction, drugs are available only through a prescription from a veterinarian. If a trainer is getting them through another source, there’s potential trouble; but that’s for another story. Supplements are available in tack shops and/or online and do not require a veterinary prescription. 

Ravit, in response to how common it is to see supplements making drug claims contrary to regulations, only said, “It cannot be quantified.” That’s “Governmentese” for “It’s anybody’s guess.”

HISA/HIWU’s own definition of a drug, by the way, is this:

“Under the Federal Food, Drug, and Cosmetic Act, the term “drug” means a product intended for use in the diagnosis, cure, mitigation, treatment, or prevention of disease, and articles other than food intended to affect the structure or any function of the body.” That’s a mouthful to say it ought to work.; you should get results.

In case you’re wondering why supplements are not regulated by the FDA, the category name “dietary supplements” gives you the answer. The FDA defines them as a “dietary ingredient intended to supplement the diet.” Dietary supplements are not regulated for humans either.

Are they safe? You would think, given the absence of regulation, the answer would be an automatic “yes.” The FDA, however, can take action to remove supplements from the market if they are adulterated (unsafe) or misbranded (misleading). Let the buyer beware.

What a trainer can control are things to avoid, such as mixing supplements with drugs, administering too many supplements, or substituting supplements for drugs altogether. 

HIWU’s language on dietary supplements is actually a bit scary:   

“It is…the responsibility of the manufacturer to ensure the product’s safety and to market the supplement in accordance with applicable law.“

The second part of the statement should give one pause. Yes, the manufacturer is responsible for the product’s safety, but it’s the trainer or trainer’s barn help that is the last person in the literal food chain for the horse. Once a supplement is in a trainer’s hands, he or she is on their own. The safe bet is a veterinarian’s assessment of any risks and/or benefits. 

HIWU addresses this in their literature: “Supplements can interact with some medication with adverse health conditions” advising trainers to “be vigilant and discuss administration [of a supplement] with your veterinarian.”

Ravit also responded with “no comment“ to whether there have already been instances of a supplement producing a positive test for an illegal or controlled substance.

Practicing veterinarians like Dr. Rick Fischer, who has been on the racetrack for 53 years, is, as one would expect, well-versed in the difference between a drug and a supplement. He presents another issue that threatens the health and safety of horses. He and other vets are not always gatekeepers with supplements for trainers. Laymen or salesmen will approach trainers directly promoting supplements. “Worse than that, they’ll give them away: ‘Here are two gallons of this. Use it and see if you like it.’ You really don’t know what the hell you’re getting,” said Fischer.

There are other words on supplements to be mindful of. HIWU’s website warns that “’natural’ does not mean safe, nor does it mean that a product is free of Prohibited Substances.  Neither do “seals of quality assurance” that guarantee a supplement is safe and effective. In short, even practicing veterinarians recommending supplements cannot guarantee safety or effectiveness.

Fischer said there have been instances where a supplement and an approved medication have produced positive tests for banned substances. 

 HIWU’s website advises, “It is crucial to have specialized knowledge from a chemical engineer or pharmacist in order to comprehend and forecast the resulting molecules, due to the intricate interplay between the chemicals involved.” 

 Fischer expounds on the “intricate interplay” thusly: “There’s been positive tests on things that I’ve never even heard of. It’s not something that anybody in their right mind would give a horse. But the chemical breakdown when they’re in combination…who knows? 

“They’ll give you a list of all the different ingredients. Most of it is Greek to these guys and some of it is Greek to me, and I’ve been practicing for more than 50 years.”

Fischer actually parroted HIWU language in saying it would take a chemical engineer or pharmacist to be able to tell “if this molecule matches up with this molecule and what it’s going to come out as.“

Good luck to any trainer looking for a chemical engineer or pharmacist on the backside. 

Dr. Day’s Black Drink, by the way, would not pass muster as a supplement as it claimed to treat colic. As for “gripes,” there is no supplement or drug for that. 

The use of 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 diarrhea, 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 feces 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 diarrhea 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 fecal 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 organizational structure of the bacterial populations can take many years to re-establish the original structure map that was laid out in treating the pre-antibiotic gut. 

Equine studies certainly show similarities to 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 seven-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 harboring 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 unfavorable 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 minimized 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 diarrhea 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 defense 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), if they’re not the best course (presence of extended-spectrum -β-lactamase (ESBL) producing  organisms) or if they’re not 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 fecal microbiota 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 Organization (FAO) and the World Health Organization (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 diarrhea—to prevent diarrhea (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. It is now being recognized 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 colonization 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 restabilizing the commensal gut microbiota; 3) protecting the intestinal epithelial barrier; 4) inducing an immune response.

It is known that there are 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 consequences 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’s large gastrointestinal populations. Regulation is lacking regarding labeling 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 minimize the introduction of antibiotic-resistant bacterial strains in the gut, and in turn, protect future antibiotic efficacy. 

How the gut-brain connection affects the performance of horses

Diligence is the mother of good luck. –Benjamin Franklin

Article by Scott Anderson

Trainers are always looking to gain an edge in performance. At a minimum, they make sure their athletes get proper nutrition and exercise. Horses require muscle and stamina to compete, so they need to be in top physical condition. But what about their mental state? Are they jittery, distracted or disinterested? No matter how strong the horses are, 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, called 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 colonizes the entire GI tract but is largely concentrated in the hindgut, where it works to ferment the prebiotic fiber in forage. The microbial fermentation of fiber 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 skeptical 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 behavior. 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 fecal 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 neighboring 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. Subsequent 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 behaviors.

Short-chain fatty acids

When microbes consume proteins and fiber, 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 that 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, which is crucial to athletic performance, as well as for 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 fiber, especially when high-energy, low-fiber 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 defense 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. The 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 behavior – 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 behavioral 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 behaviors (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 behavior 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 behavior was positively correlated with Pseudomonas and negatively correlated with Anaeroplasma. 

Some of these behaviors 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 subside on low-energy, high-fiber 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 that 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. Introducing new feeds slowly helps to prevent overgrowth and allows a balanced collection of microbes to acclimate to a new regimen. 

Stress. Training, trailering 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 diarrhea, 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 fiber to optimize 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 – The key to a well-balanced equine gut

Article 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.  

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.

Figure 1: Factors that can lead to gut dysbiosis

What exactly is a probiotic?

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.

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.

Racehorse Bone Health: From a Nutritional Perspective

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. 

By Louise Jones

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.

Can we increase the efficiency of the digestive system through dietary and supplementary manipulation in order to alter performance and recovery?

No guts - no glory!

By Catherine Rudenko

The idiom ‘no guts, no glory’, when taken in the literal sense, is quite an appropriate thought for the racehorse. The equine gut is a collection of organs, which when in a state of disease, causes a multitude of problems; and when functioning effectively, it is key for conversion of food to fuel and maintaining normal health. 

In the same way we consider how fuel-efficient our car engines are, what power can be delivered and the influence of fuel quality on function, we can consider the horses’ digestive anatomy. The state of the ‘engine’ in the horse is critical to the output. What is fed or supplemented, and the manner in which we do so, has fascinating and somewhat frightening effects on efficiency and recovery. 

We now, in a human context, have a much better understanding of the relationship between the gut and states of disease. Before disease in a notable sense is present, we see loss of function and reduction in performance. With equines, in recent years, the focus has fallen toward ulceration and the stomach. Now interest is growing into the small and large intestines, looking at factors that influence their performance and in turn how this affects performance on the track. 

In order to consider how we can positively influence gut function, first we need to understand its design and capability, or lack of capability which is more often the problem. The horse, by definition, falls into the category of a large non ruminant herbivore—the same grouping as rhinoceroses, gorillas and elephants. The horse is well designed for a fibre-based diet, as reflected by the capacity of the large intestines, yet we must rely heavily on the small intestine when feeding racehorses. Health and function of both small and large intestines are important and are connected. 

Small Intestine 

The small intestine is a relatively short tube of approximately 25m in length—the same length as found in sheep or goats. The primary role of the small intestine is the digestion of protein, fats and carbohydrates. The workload of this organ is significant and is also time constrained, with feed typically moving at a rate of 30cm per minute (1). The rate of passage is highly influenced by whether the stomach was empty before feeding, or if forage has recently been consumed. The advice of feeding chaff with hard feed is in part to the slow rate of passage and give further time for the processes of digestion. 

The mechanisms for digestion in the small intestine include pancreatic juices, bile and enzymes. Of particular interest are the various enzymes responsible for digestion of protein and carbohydrates— the key nutrients often considered when choosing a racing diet. The ability to digest carbohydrate, namely starch, is dependent on two factors: firstly, form of starch and the level of alpha-amylase—a starch-digesting enzyme found in the small intestine. Whilst the horse is quite effective in digestion of protein, there are distinct limitations around digestion of starch. 

Starch digestion, or lack of digestion in the small intestine, is the area of interest. When feeding, the aim is to achieve maximum conversion of starch in the small intestine to simple sugars for absorption. This is beneficial in terms of providing a substrate readily available for use as an energy source and reducing the ill effects seen when undigested starch moves into the next section of the digestive tract. Alpha-amylase is found in very limited supply in the equine small intestine—the amount present being only approximately 5% of that found within a pig. Despite a low content, the horse can effectively digest certain cereal starches, namely oats, quite effectively without processing. However, other grains commonly used, (e.g., barley and maize [corn]), have poor digestibility unless processed. Flaked, pelleted or extruded cereals undergo a change in starch structure enabling the enzyme to operate more effectively. 

Processing grains whilst improving digestion does not alter the amount of enzyme present in the individual. An upper limit exists on starch intake, after which the system is simply overloaded and the workload is beyond the capacity of the naturally present enzymes. The level is estimated at 2g starch per kilogram of bodyweight in each meal fed. In practice, this translates to 3.5kg (7 ¾ lbs) of a traditional grain-based diet of 28% starch. In bowls, this is roughly 2 bowls of cubes or 2 ¼ bowls of mix—an intake typical of an evening feed. The ‘safe limit’ as a concept is questionable because of other factors involved in starch digestion, including how quickly a horse will eat their feed, dental issues and individual variation in the level of alpha-amylase present. 

In practice, feeding racehorses will invariably test the capacity of the small intestine as the volume of feed required to meet the demands of training is significant, and through time constraints of both horse and human results in a large-sized evening meal. The addition of amylase or other enzymes to the diet is therefore of interest. Addition of amylase is documented to increase digestion of maize (corn)—one of the most difficult grains to digest—from 47.3% to 57.5% in equines (2). Equally, wheat digestion has been evidenced to improve with a combination of beta-glucanase, alpha-amylase and xylanase in equines, increasing starch digestion from 95.1% to 99.3% (3).

Use of enzymes in the diet has two areas of benefit: increasing starch conversion and energy availability, and reducing the amount of undigested starch that reaches the hindgut. The efficacy of the small intestine directly impacts the health of the large intestine—both of which influence performance. 

photo credit threeoaksequine.com

Large Intestine 

The caecum and colon, of which there are four segments, form the group referred to as the hindgut. Their environment and function are entirely different to that of the small intestine. Here, digestion is all about bacterial fermentation of the fibrous structures found in forages and parts of grains and other feed materials. The time taken to digest foodstuffs is also significantly different to that of the small intestine, with an average retention time of 30 hours. 

The end result of fermentation is the production of fatty acids, namely acetate, butyrate and propionate—the other by-product of fermentation being lactate. The level of fatty acids and lactate produced is dependent on the profile of bacteria found within the gut, which in turn react to the type of carbohydrate reaching the hindgut. There are markedly different profiles for horses receiving a mostly fibre-based diet compared to those with a high-grain intake. 

The interaction between the microbial organisms and metabolism, which directly influences health and disease, is gaining greater understanding. By looking at the faecal metabolome, a set of small molecules that can be identified in faecal samples, and the categories of bacteria in the gut, it is possible to investigate the interaction between the individual horse, its diet and bacteria. Of course, the first challenge is to identify what is normal or rather what is typical of a healthy horse so that comparatives can be made. Such work in horses in training, actively racing at the time of the study, has been carried out in Newmarket. 

Microbiome is a term used to describe microorganisms, including bacteria, that are found within a specific environment. In the case of the horses in training, their microbiome was described before and after a period of dietary intervention. The study evidences the effect on the hindgut of including an enzyme supplement, ERME (Enzyme Rich Malt Extract). The table below shows changes in nine bacterial groups before and after supplementation. 

Linear discriminant analysis indicating significant differences in relative abundance of nine bacterial genera before and after supplementation. Red bars show greater abundance before supplementing, and green bars show greater abundance after supplementing. (4)

Along with changes in bacterial abundance, which were relatively small, came more significant changes within the metabolome. The small molecules found in the metabolome are primarily acids, alcohols and ketones. Of particular interest, and where statistical significance was found, were changes in acetic acid and propionic acid evidencing an effect on the digestive process. 

Whilst production of fatty acids is desired and a natural outcome of fermentation, further work is needed to determine what is an optimum level of fatty acid production. This study of horses in training is an interesting insight into an area of growing interest. 

Changes in abundance of acetic and propionic acid in 6 thoroughbred horses following dietary supplementation with malt extract. 0 = horses before supplement, 1 = horses after supplementation (4)

Effects on Performance & Large Intestine Function

We know that starch should ideally be digested in the small intestine and have evidence as to some of the ill effects seen when large quantities reach the large intestine. It is accepted that dietary changes influence microbial changes, and such changes are related to health status in many species. What is less well documented is the direct effect on the performance of manipulating starch digestion. It is logical to assume good health equals good performance, but data is scarce as to whether dietary manipulation could really be performance enhancing. 

For the above-mentioned enzyme supplement, a field study to consider effects on performance took place following a flat yard—a minimum of 35 horses—over three seasons. The study was based on Timeform racing performance of the individuals and then averaged across the yard for each season. The three seasons of 2013, 2014 and 2015 whilst supplemented were compared to the three previous years from 2010-2012 where no supplemented was given. The average rating increased from 83.0 to 89.2 across the yard. Field studies are always challenging, having a control group without supplementation is not always practical, and so as in this case, the study is for all horses over a period of time to compare the whole yard’s performance. The results of this study are positive in terms of identifying an effect of dietary intervention and monitoring of performance. 

Changes in average Timeform rating for years without supplementation (2010-2012) and years with supplementation of enzymes from malt extract (2013-2015). (12)

Other approaches to influencing bacterial profile are through the use of probiotics and prebiotics, and these are already commonly found in the feed room. Probiotics include bacteria and yeasts designed to promote the development of ‘beneficial’ bacteria in the gut. Prebiotics are also frequently supplemented and include specific sugars, namely FOS (fructo oligosaccharides) and MOS (mannan oligosaccharides). Their use is recommended where gut health is challenged, or poor health already exists, as the benefit to a healthy thriving gut is questionable. Racehorses, through the training and feeding regimes required, are considered to operate in a challenging environment and so use is likely warranted. 

The probiotics Lactobacillus species (bacteria) and saccharomyces cerevisiae (yeast) have been proven to survive the acidic environment of the stomach and successfully progress to the large intestine. Yeast is documented to improve digestion, specifically of dry matter and the minerals magnesium, potassium and phosphorus (5). In terms of performance, evidence exists for studs around improved milk quality and foal growth (6,7). Yeast is often supplemented within racing diets, although not all brands include this probiotic as standard. Lactobacillus has been considered more from a stud perspective looking at its role in reducing diarrhoea in foals.

FOS as a prebiotic has reports of clinical benefits related to reducing the incidence of colic (8) and is proven to modify the balance of bacteria found in the large intestine (9). Aside from direct benefits to the hindgut itself, studies are proving links between immune response and gut profile when supplemented. Studies in pigs and broilers have evidence improved immune response when supplemented with FOS, and an initial equine study looks promising although more work is needed (10).

MOS operates in a different manner to FOS, helping to reduce pathogen adherence to the intestine lining. Its beneficial effects come from the ability to safely bind and eliminate certain pathogens from the gut. MOS as a substance is used in many species including humans, dogs, poultry and equines. It too can influence immune response, and most work focuses on influencing the mother and her offspring in various species. In equines, mare IgA and colostrum IgA, IgM and IgG antibodies have been evidenced to improve following supplementation (11).

Summary 

The health status and efficacy of both the small and large intestine are of significance when considering performance. Whether directly monitoring the effect of a dietary intervention on racing results, the improvement of nutrient conversion, the microbiome, immune response or effect on presence of pathogens, the manner in which we feed and what we supplement is of importance. 

Use of enzymes, prebiotics or probiotics is an area that warrants consideration when looking at how to get more from the gut and also when wanting to reduce the risk of colic or presence of pathogens. Each of these categories of supplements has a different mode of action, and so one is not per se better than another. There is still more needed in terms of equine-specific research, particularly around direct links to on-track performance following supplementation, but what is there is promising, and the benefits already documented are relevant and worthy of attention. 

References 

1. Frape,D. (2010) Equine Nutrition and Feeding (4th Edition) West Sussex: Wiley-Blackwell

2. Meyer,H., Radicke,S., Kienzle,E., Wilke,S., Kleffken,. Illenseer,M. (1995) Investigation on Preileal Digestion of Starch from Grain, Potato and Manioc in Horses. Transboundary and Emerging Diseases 42:371-381.

3. Rowe,L.,Brown,W.,Bird,S. (2001) Safe and Effective Grain Feeding for Horses. Rural Industries Research Development Corporation. 

4. Proudman,C.J., Hunter,J.O., Darby,A.C., Escalona,E.E., Batty,C., Turner,C. (2014) Characterisation of the fecal metabolome and microbiome of Thoroughbred racehorses. Equine Veterinary Journal pp 1-7.

5. Pagan,J.D. (1990 ) Effect of yeast culture supplementation on nutrient digestibility in mature horses. Kentucky Equine Research Conference 2018 Proceedings p137.

6. Glade, M. J. (1991). Dietary yeast culture supplementation of mares during late gestation and early lactation: effects on dietary nutrient digestibilities and fecal nitrogen partitioning. Journal of Equine Veterinary Science 11(1): 10-16. 

7. Glade, M. J. (1991). Effects of dietary yeast culture supplementation of lactating mares on the digestibility and retention of the nutrient delivered to nursing foals via milk. Journal of Equine Veterinary Science 11(6): 323-329.

8. Julliand,v. (2006) Pre-and Probiotics: Potential for Equine Practice. Proceedings of the 3rd European Equine Nutrition & Health Congress.

9. Respondek,F., Goachet,A.G. Julliand,V. (2008) Effects of short-chain fructooligosaccharides on the intestinal microflora of horses subjected to a sudden change in diet. Journal Animal Science 86: 316-323.

10. Apper,E. Favire,L. Goachet,A.G., Respondek,F. Julliand,V. Fermentative Activity and Immune Response of Horses fed with scFOS followed by vaccination: a preliminary study. Tereos poster presentation at Agro Sup Dijon. 

11. Spring,P., Wenk.c., Connollys,A., Kiers.A. (2015) A review of 733 published trials on Bio-Mos, a mannan oligosaccharide, and Actigen, a second generation manna rich fraction, on farm and companion animals. Journal of Applied Animal Nutrition 3:1-11.

12. Hunter,J.O. & Cumani,L. (2015) Field study of horses in training supplemented with ERME (Enzyme Rich Malt Extract). Unpublished. 

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

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.

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. Some studies report a lower risk of ESGD when pasture in company is provided for horses in training, whereas others have found no significant effect. The duration of access and quality of pasture involved may be part of the differences in results found. There is a distinct difference between turnout in a paddock that offers a pick of grass and a leg stretch and a paddock rich in well managed pasture. Ultimately a period of turnout whilst in a training program is not enough of a counter-balance to the risks of frequent and intense exercise, coupled with a need for stabled periods and higher rates of compound feeding.

CLICK HERE to return to issue contents or sign up below to read this article in full

Small but mighty - the role of antioxidants for horses in training

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.

Oxidative stress

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. …

CLICK HERE to return to issue contents or sign up below to read this article in full

BUY THIS ISSUE IN PRINT OR DOWNLOAD

ISSUE 60 (PRINT)

$6.95

ISSUE (DIGITAL)

$3.99

WHY NOT SUBSCRIBE?

DON'T MISS OUT AND SUBSCRIBE TO RECEIVE THE NEXT FOUR ISSUES!

Four issue subscription - ONLY $24.95



“Bon Appétit” - how to encourage and maintain appetite throughout the season

By Catherine Rudenko

Encouraging and maintaining appetite throughout aseason can become a serious challenge. The best planned feeding program in the world is of no use if the horse simply does not eat as required to sustain performance. There are multiple factors that can lead to poor appetite for horses in training – some relating to health, some relating to physical properties of the feed or forage, along with behavioral considerations.

What is a normal appetite?

Grain-based feeds are an important requirement for a horse in training.

Before we can fairly state a particular horse has a poor appetite, we must first have an idea of what a normal appetite range is. The horse has a given capacity within its digestive tract and an appetite appropriate to this. Horses will typically consume 2-3% of their body weight each day on a dry matter basis – in other words not accounting for fluid intake or any moisture found in the forages. This equates to 10-15kg (or 22-33lbs) per day for a 500kg-weight (or 1100lb) racehorse. As fitness increases, it is normal for appetite to reduce, and most horses will eat closer to 2% of their body weight. The energy requirement of a horse in training is such that they dependent on a large amount of grain-based “hard feeds,” which for the majority form 7-9kg (or 15-19lbs) of the diet each day. With a potential appetite of 10-15kg (or 22-33lbs) we are, for some individuals, running close to their likely appetite limit. The most immediate effect of a reduction in appetite is the reduction in energy intake. Horses require a large amount of calories, typically 26,000 to 34,000 cal per day when in full training. Comparatively, an average active human will require only 3,000 cal per day. Just one bowl of a racing feed can contain 4,500 cal, and so feed leavers that regularly leave a half or quarter of a bowl at each meal time really can be missing out. Forage is equally a source of calories, and a reduction of intake also affects total calorie intake.

• Physical form of feed and forage

The physical form of the bucket feed can affect feed intake due to simple time constraints. Morning and lunch time feeds are more common times at which to find feed left behind. Different feed materials have different rates of intake – due to the amount of chewing required – when fed at the same weight. To give an example, 1kg (or 2lbs) of oats will take 850 chews and only 10 minutes to consume in comparison with 1kg of forage taking up to 4,500 chews and 40 minutes to consume. Meals that require a high amount of chewing – while beneficial from the point of view of saliva production (the stomach’s natural acid buffer – can result in feed “refusal” as there is simply too much time required. Cubes are often eaten more easily as they are dense, providing less volume than a lighter, “fluffier” coarse mix ration. Inclusion of chaff in the meal also slows intake, which can be beneficial, but not for all horses. Any horse noted as a regular feed leaver ideally needs smaller meals with less chewing time. Keeping feed and forage separate can make a significant difference. The choice of forage is important for appetite. Haylage is more readily consumed, and horses will voluntarily eat a greater amount. The study below compares multiple forage sources for stabled horses. Another factor relating to forages is the level of NDF present. NDF (neutral detergent fiber) is a lab measure for forage cell wall content – looking at the level of lignin, cellulose and hemi-cellulose. As a grass matures, the level of NDF changes. The amount a horse will voluntarily consume is directly related to the amount of NDF present. Analyzing forage for NDF, along with ADF, the measure relating to digestibility of the plant, is an important practice that can help identify if the forage is likely to be well received. Alfalfa is normally lower in NDF and can form a large part of the daily forage provision for any horse with a limited appetite. As alfalfa is higher in protein – should it become a dominant form of daily fiber – then a lower protein racing feed is advisable. Racing feeds now range from 10% up to 15% protein, and so finding a suitable balance is easily done.

• B vitamins

B vitamins are normally present in good quantity in forages, and the horse itself is able to synthesize B vitamins in the hindgut. Between these sources a true deficiency rarely exists. Horses with poor appetite are often supplemented with B12 among other B vitamins. Vitamin B12 is a cofactor for two enzymes involved in synthesis of DNA and metabolism of carbohydrates and fats. Human studies where a B12 deficiency exists have shown an improvement in appetite when subjects were given a daily dose of B12.(3) As racehorses are typically limited in terms of forage intake and their hindgut environment is frequently challenged, through nutritional and physiological stresses, it is reasonable to consider that the racehorse, while not deficient, may be running on a lower profile. Anecdotal evidence in horses suggests B12 supplementation positively affects appetite as seen in humans. Another area of interest around B vitamin use is depression. Horses can suffer from depression and in much the same way as in the human form, this can affect appetite. …

CLICK HERE to return to issue contents or sign up below to read this article in full

ISSUE 59 (PRINT)

$6.95

ISSUE 59 (DIGITAL)

$3.99

WHY NOT SUBSCRIBE?

DON'T MISS OUT AND SUBSCRIBE TO RECEIVE THE NEXT FOUR ISSUES!

Four issue subscription - ONLY $24.95

Can nutrition influence EIPH? - 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.

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

Kentucky Equine research results

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.

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. …

CLICK HERE to return to issue contents

ISSUE 58 (PRINT)

$6.95

ISSUE 58 (DIGITAL)

$3.99

WHY NOT SUBSCRIBE?

DON'T MISS OUT AND SUBSCRIBE TO RECEIVE THE NEXT FOUR ISSUES!

Four issue subscription - ONLY $24.95

Nutrition - how to rein in your complex carb intake for times when work drops

By Catherine Rudenko

Carbohydrates are by far the largest component of any horse’s diet, typically two thirds by weight, yet we often focus more on other nutrients, such as protein—which in comparison forms only a small portion of the total diet at around 8-13%. Carbohydrates, specifically the balance between differing carbohydrate sources, influences three key areas relating to performance.

The choice of carbohydrate influences the type of energy available, providing varying proportions of ‘fast release’ or ‘slow release’ energy. The type of carbohydrate chosen also impacts behaviour, increasing or decreasing risk of excitability and certain stereotypical behaviours. Last, but by no means least, the choice of carbohydrate and the way in which it is fed impacts digestive health and the ability of the digestive system to convert food to ‘fuel’ for the body.

Getting the balance right between the different types of carbohydrates is important for getting the right results when having to adjust the intensity of training, when resting a horse and when working back up through the stages of fitness. 

What are carbohydrates? 

There are different ways of classifying or grouping carbohydrates, depending on whether you take things from the plant’s point of view or that of the digestive anatomy of the horse. Working with the horse in mind, carbohydrates are best classified by the section of the digestive system that they are processed in—either the small intestine or large intestine. The site of digestion determines the type of energy provided, often referred to as fast releasing for the small intestine and ‘slow releasing’ for the large intestine. The group of carbohydrates, known as hydrolysable carbohydrates, are the group behind the description of fast releasing, whilst the group known as fermentable carbohydrates are those forming the ‘slow releasing’ category. Within the fermentable group, there are three sub groups of rapid, medium and slow. 

What are carbohydrates made of? 

There are many types of carbohydrates in the horse’s diet, ranging from simple sugars to more complex structures. They are defined by their degree of polymerisation, which refers to the way in which sugar units are joined together. How a carbohydrate is formed and the type of link present are important as they determine if digestion is possible in the small intestine or whether fermentation in the large intestine is required. This influences the type of energy available. 

For horses in training, the type of carbohydrate of particular interest is the polysaccharide group which includes starch, cellulose, hemicellulose and fructans amongst others. Starch is found in significant quantities in hard feeds, whilst cellulose and hemicellulose, amongst other fermentable carbohydrates are abundant in forages. Pasture is a source of fructans, which can change rapidly depending on growing conditions and daylight hours. 

Structure

Single sugars, also called simple sugars, comprise one unit only. They are categorised as monosaccharides—the most commonly known being glucose. For horses in training this is a highly valuable sugar as it is the main ‘fuel’ for muscles. Glucose forms the basis of many of the more complex structures of interest to horses in training.

When two sugars join together, they are known as a disaccharide—the best known being lactose which is found in mare’s milk. Oligosaccharides refer to more complex structures where more units are joined together—a common example being fructo-oligosaccharide (FOS) which many horses in training are specifically fed as a prebiotic to support digestive function. 

Type of Carbohydrate

Polysaccharides, our group of particular interest, are significantly more complex chains that are branched and are not so easily digested as the simple sugars. The branched nature of polysaccharides, such as starch and cellulose, are the result of links between chains of sugars. The type of link present determines whether or not it will be possible for the horse to digest this form of carbohydrate in the small intestine or not.

Starch



Starch is the primary carbohydrate of interest in our hard feeds. It is a hydrolysable carbohydrate, which can be digested in the small intestine, releasing glucose into the bloodstream. For horses in training this is the most important fast release energy source. Starch is found in all plants, with the highest quantities seen in cereals such as oats, barley and maize.

Composition of cereals commonly used in racing feeds

Starch is made up of two types of sugar chains: amylose and amylopectin, which are formed from glucose units. Amylose itself is easily digested, however amylopectin has a different type of bond connecting each branch, which the enzymes of the small intestine cannot break down. Feed processing, which changes the structure of starch and breaks apart the previously indigestible bonds, is therefore a key factor in ensuring that when starch is fed that the maximum amount of glucose is derived. 

Amylose and Amylopectin 

Feed processing comes in many forms, from simply crushing or rolling the grain to cooking techniques including micronizing, steam flaking, pelleting or extruding. The amount of processing required for what is deemed efficient digestion differs by grain type. Oats have a natural advantage within the cereal group as they can be fed whole, although processing can still improve digestion. Barley, wheat and maize cannot be fed whole or simply rolled. They require cooking to ensure that starch becomes available, and the impact of cooking processes is much greater for these grains. 

The availability of starch is assessed through the amount of glucose released into the blood after feeding. The study below shows the effect of steam cooking maize (corn) compared to two processes that simply change the physical appearance, cracking or grinding. Steam-flaked maize is more available as shown by the greater glucose response. 

Starch is a fast release energy source, being digested in the small intestine, and the term can easily be misunderstood. It does not mean that the horse will suddenly run at top speed nor appear to be fuelled by ‘rocket fuel’. The word ‘fast’ relates to the relatively short time it takes for digestion to occur and glucose to be available. …

CLICK HERE to return to issue contents

ISSUE 57 (PRINT)

$6.95

ISSUE 57 (DIGITAL)

$3.99

WHY NOT SUBSCRIBE?

DON'T MISS OUT AND SUBSCRIBE TO RECEIVE THE NEXT FOUR ISSUES!

Four issue subscription - ONLY $24.95

The Balancing Act - feed - supplement

By Catherine Rudenko

Key considerations when reviewing what you feed and if you should supplement

With so many feeds and supplements on the market, the feed room can soon take on the appearance of an alchemist’s cupboard. Feeding is of course an artform but one that should be based on sound science. In order to make an informed decision, there are some key questions to ask yourself and your supplier when choosing what ingredients will form your secret to success.

QUESTION #1: What is it?

Get an overview of the products’ intended use and what category of horse they are most suited for. Not every horse in the yard will require supplementing. Whilst one could argue all horses would benefit from any supplement at some level, the real question is do they need it? Where there is a concern or clinical issue, a specific supplement is more likely warranted and is more likely to have an impact. A blanket approach for supplements is really only appropriate where the horses all have the same need (e.g., use of electrolytes).

QUESTION #2: Is it effective?

There are many good reasons to use supplements with an ever-increasing body of research building as to how certain foods, plants or substances can influence both health and performance. Does the feed or supplement you are considering have any evidence in the form of scientific or clinical studies? Whilst the finished product may not—in a branded sense—be researched, the active components or ingredients should be. Ideally, we look for equine-specific research, but often other species are referenced, including humans; and this gives confidence that there is a sound line of thinking behind the use of such ingredients. Having established if there is evidence, the next important question is, does the feed or supplement deliver that ingredient at an effective level? For example, if research shows 10g of glucosamine to be effective in terms of absorption and reaching the joint, does your supplement or feed—when fed at the recommended rate—deliver that amount?

There is of course the cocktail effect to consider, whereby mixing of multiple ingredients to target a problem can reduce the amount of each individual ingredient needed. This is where the product itself is ideally then tested to confirm that the cocktail is indeed effective.

QUESTION #3: How does it fit with my current feeding and supplement program?

All too often a feed or supplement is considered in isolation which can lead to over-supplementing through duplication. Feeds and supplements can contain common materials, (i.e., on occasion there is no need to further supplement or that you can reduce the dose rate of a supplement). Before taking on any supplement, in addition to your current program, you first need to have a good understanding of what is currently being consumed on a per day basis. This is a different matter of comparing one feed tag or supplement pot to another one. Such ‘direct’ comparisons are rarely helpful as dose rates or feeding rates differ, and the manner in which units are expressed is often confusing. Percentages, grams, milligrams and micrograms are all common units of measure used on labeling. The unit chosen can make an inclusion sound significant when perhaps it is not. For example, 1g could be expressed as 1,000mg. Looking at the contribution, any feed or supplement made on an as-fed basis is the only way to know the true value for the horse. There are many categories of supplements in the market with the greatest cross-over existing around use of vitamins or minerals, which appear in both feeds and supplements. Occasionally feeds can also be a source of ingredients used in digestive health supplements or joint supplements. The contribution of your chosen feed(s) is the base from which you decide what, if any, of those matching nutrients or ingredients should be added to. Common areas for cross-over include vitamin E, selenium, B vitamins, iron, magnesium, calcium, phosphorus, zinc and copper. Duplication may also occur around use of vitamin C (antioxidant), FOS (prebiotic), MOS (pathogen binder), yeast (prebiotic) and occasionally maerl (marine algal calcium source).

Vitamins and Minerals An often-seen addition to the feed program for Thoroughbreds are bone supplements—providing relevant minerals such as calcium, phosphorus, zinc and copper. Whilst unquestionably important for sound skeletal development these nutrients are also present in feed, albeit at slightly varying levels by brand. Below is a typical profile of a bone supplement with the information as seen per kilogram on the feed label. Calcium and phosphorus are given as percentages on labels and require converting to grams when looking to calculate the amount of nutrients consumed. In this example, the calcium content is 20%, equivalent to 200g per kilogram.

The feeding rate is 31⁄2oz per horse per day. …

CLICK HERE to return to issue contents

BUY THIS ISSUE IN PRINT OR DOWNLOAD

ISSUE 56 (PRINT)

$6.95

ISSUE 56 (DIGITAL)

$3.99

WHY NOT SUBSCRIBE?

DON'T MISS OUT AND SUBSCRIBE TO RECEIVE THE NEXT FOUR ISSUES!

Four issue subscription - PRINT & ONLINE - ONLY $24.95

Testosterone - More than just muscles

By Dr Catherine Dunnett

Testosterone is a hormone that has received a lot of attention in the media, mostly in a negative context due to its historical doping use in humans and animals.  When we think about testosterone we associate it with muscle building and aggression. There is, however, so much more to testosterone, which I have uncovered in recent weeks.  

Testosterone is a hormone that is produced naturally by colts, fillies and geldings in varying amounts. Colts show a naturally higher circulating level of testosterone than geldings and fillies. Testosterone is classified as a steroid hormone, and it has a characteristic ring-like structure, being ultimately derived from cholesterol (see Figure 1).  It is produced primarily in the testes in colts, but perhaps surprisingly also in the ovaries and adrenal glands, which explains the natural levels found in fillies and geldings.  

Testosterone is responsible for the development of primary sexual characteristics in males and also drives muscle development. However, it is also converted to dihydrotestosterone and estradiol, both of which have interrelated functions.  Estradiol has a major role to play in the brain and in maintaining cartilage integrity and bone density. Interestingly, neither synthetic testosterone, nor dihydrotestosterone can be converted to estradiol; and so this is likely to have negative connotations for bone when the muscular strength is affected through synthetic testosterone administration.

Testosterone also has an effect on blood by stimulating the production of red blood cells. It is also reputed to have a psychological impact beyond the well-recognized effects on sexual drive and aggression.  In people, testosterone is reported to boost confidence and positivity in some circumstances, as well as dominance and competitive success.

Testosterone synthesis is not straightforward and forms part of a complex series of pathways where cholesterol can be converted to one of many possible steroidal substances. How much testosterone is produced is controlled by a series of hormones and various feedback mechanisms. Stimulation of testosterone synthesis would be difficult to achieve non-medically, yet it has been a target of supplement manufacturers in humans and horses over many years.  Ingredients such as gamma oryzanol, fenugreek, ginseng, velvet antler, horny goat weed and others have been offered as having a positive effect on testosterone synthesis. Most of these ingredients, however, would have little in the way of science to support this and even where some published studies exist. For example, for extracts of fenugreek, there is significant controversy over the validity of the results. Additionally, one can never be sure that a positive result in one species will deliver the same in another species due to differences in digestion and absorptive capacity, as well as physiological differences.  As far as I am aware, there are no ingredients or products that have been unequivocally shown to boost circulating testosterone in horses.

Rice bran oil

One such ingredient—gamma oryzanol—is a nutritionally important constituent of rice bran oil and is normally present at a level of about 1-2%.  Gamma oryzanol is sometimes marketed as a “natural steroid” with the ability to increase circulating testosterone naturally. Gamma oryzanol is in fact not a single compound but a mixture of ferulic acid esters of triterpene alcohols and plant sterols. 

Gamma oryzanol has been used in both human and equine athletes in the belief that it elicits anabolic effects, ranging from increased testosterone production and release, to stimulating growth hormone release. …

BUY THIS ISSUE IN PRINT OR DOWNLOAD

ISSUE 55 (PRINT)

$6.95

ADD TO CART

ISSUE 55 (DIGITAL)

$3.99

ADD TO CART

WHY NOT SUBSCRIBE?

DON'T MISS OUT AND SUBSCRIBE TO RECEIVE THE NEXT FOUR ISSUES!

Four issue subscription - PRINT & ONLINE - ONLY $24.9

ADD TO CART

Thoroughbred nutrition past & present

By Catherine Rudenko

Feeding practices for racehorses have changed as nutritional research advances and food is no longer just fuel but a tool for enhancing performance and providing that winning edge. 

While feeding is dominantly considered the content of the feed bucket, which by weight forms the largest part of the horse’s diet, changes in forage quality have also played a role in the changing face of Thoroughbred nutrition. The content of the feed bucket, which is becoming increasingly elaborate with a multitude of supplements to consider, the forages—both long and short chop and even the bedding chosen—all play a part in what is “the feed program.” Comparing feed ingredients of the past against the present provides some interesting insights as to how the industry has changed and will continue to change.

Comparing key profiles of the past and present 

The base of any diet is forage, being the most fundamental need of the horse alongside water. Forage quality and form has changed over the years, particularly since haylage entered the market and growers began to focus specifically on equine. The traditional diet of hay and oats, perhaps combined with mash as needed, provided a significantly different dietary intake to that now seen for horses fed a high-grade haylage and fortified complete feed. 

Traditional Diet

• 7kg Oats

• 1kg Mash – comprised of bran, barley, linseed and epsom salt

• 0.5kg Chaff

• Hay 6% protein consumed at 1% of bodyweight

Modern Diet – medium-grade haylage

• 8kg Generic Racing Mix 

• 0.5kg Alfalfa Chaff

• 60ml Linseed Oil

• 60g Salt

• Haylage 10% protein consumed at 1% of bodyweight

Modern Diet – high-grade haylage

• 8kg Generic Racing Mix 

• 0.5kg Alfalfa Chaff

• 60ml Linseed Oil

• 60g Salt

• Haylage 13% protein consumed at 1% of bodyweight

Oats field

The traditional example diet of straights with bran and hay easily met and exceed the required amount of protein providing 138 % equirement. When looking at the diet as a whole, the total protein content of the diet inclusive of forage equates to 9.7%. In comparison, the modern feeding example using a high-grade haylage produces a total diet protein content equivalent to 13.5%. The additional protein—while beneficial to development, muscle recovery and immune support—can become excessive. High intakes of protein against actual need have been noted to affect acid base balance of the blood, effectively lowering blood pH.1 Modern feeds for racing typically contain 13-14% protein, which complement forages of a basic to medium-grade protein content very well; however, when using a high-grade forage, a lower protein feed may be of benefit. Many brands now provide feeds fortified with vitamins and minerals designed for racing but with a lower protein content. 

While the traditional straight-based feeding could easily meet energy and protein requirements, it had many short-falls relating to calcium and phosphorus balance, overall dietary mineral intake and vitamin intake. Modern feeds correct for imbalances and ensure consistent provision of a higher level of nutrition, helping to counterbalance any variation seen within forage. While forage protein content has changed, the mineral profile and its natural variability has not. 

Another point of difference against modern feeds is the starch content. In the example diet, the “bucket feed” is 39% starch—a value that exceeds most modern racing feeds. Had cracked corn been added or a higher inclusion of boiled barley been present, this level would have increased further. Racing feeds today provided a wide range of starch levels ranging from 10% up to the mid-thirties, with feeds in the “middle range” of 18-25% becoming increasingly popular. There are many advantages to balancing starch with other energy sources including gut health, temperament and reducing the risk of tying-up. 

The horse with a digestive anatomy designed for forages has limitations as to how much starch can be effectively processed in the small intestine, where it contributes directly to glucose levels. Undigested starch that moves into the hindgut is a key factor in acidosis and while still digested, the pathway is more complex and not as beneficial as when digested in the small intestine. Through regulating starch intake in feeds, the body can operate more effectively, and energy provided through fibrous sources ensures adequate energy intake for the work required.

TO READ MORE - BUY THIS ISSUE IN PRINT OR DOWNLOAD

ISSUE 54 (PRINT)

$6.95



ISSUE 54 (DIGITAL)

$3.99

WHY NOT SUBSCRIBE?

DON'T MISS OUT AND SUBSCRIBE TO RECEIVE THE NEXT FOUR ISSUES!

Four issue subscription - PRINT & ONLINE - ONLY $24.9

Gut health - aspects of bad behavior 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 behavior resulting from a poor training foundation leading the horse to take unfamiliar or uncomfortable situations into their own hands, which 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 behavior is just in the horse’s head or that the horse is just an ill-tempered individual. In my experience, most unexplainable behavior 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, their symptoms and common protocols utilized 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 behavior. 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 center of digestive health. We now recognize 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 the development of more sophisticated techniques used to identify and measure the composition of the microbiome 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 recognize 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 behavior 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 behavior 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.

TO READ MORE —

BUY THIS ISSUE IN PRINT OR DOWNLOAD -

SUMMER SALES 2019, ISSUE 53 (PRINT)

$6.95

SUMMER SALES 2019, ISSUE 53 (DIGITAL)

$3.99

WHY NOT SUBSCRIBE?

DON'T MISS OUT AND SUBSCRIBE TO RECEIVE THE NEXT FOUR ISSUES!

PRINT & ONLINE SUBSCRIPTION

From $24.95

All about tying-up

By Catherine Rudenko

Tying-up or ER (exertional rhabdomyolysis) is a problem that every yard will encounter at some point in time with reports of 5-7% of the Thoroughbred population being affected. ER is the general term used to cover two main forms of tying-up, acute or recurrent. ER by definition relates to the breakdown of striated muscle fibers following exercise. These fibers connect to the bone allowing movement of the skeleton. Damage causes anything from mild stiffness to the inability to move.

With much still unknown about the condition, the focus falls on reducing risk and ongoing management of those affected with recurrent form. The main area for intervention and management relates to feeds and feeding practices—an area that can be directly controlled by the yard and adjusted as needed for the individuals most affected.

Acute Exertional Rhabdomyolysis

The acute form is typically caused through factors external to the muscle rather than there being an intrinsic muscle defect.

It is most commonly seen when the horse is adapting to a new level of work, and the intensity or duration is too strenuous. Where speed work is concerned, the most likely cause is a depletion of cellular high energy phosphates, the muscles’ energy supply, combined with lactic acidosis. Where endurance work is concerned, depletion of intracellular glycogen—the stored form of glucose often combined with over-heating and electrolyte imbalances—is the common cause.

The other key factor for an acute episode is dietary energy intake being excessive to the current level of work. The use of high-starch feeds to supply energy for horses in training is a common practice with grains (traditionally oats) forming the basis of such feeds. In the early stages of fitness work, an over-supply of energy relative to need, particularly when starch forms a large part of the diet, is a risk factor.

Recurrent Exertional Rhabdomyolysis

This form of ER—where episodes are frequent and often seen even at low levels of exercise—has led to the suggestion that much like humans, there is an inherited intrinsic muscle defect. Such defects would predispose the horse to ER. Documented defects relevant to Thoroughbreds include a disorder in muscle contractility or excitation contraction coupling, whereby muscle fibers become over-sensitive, and normal function is disrupted.  

Risk factors for ER in horses with the recurrent form include stress or high excitement during exercise, periods of jogging (10-30 minutes), infrequent exercise, and over-feeding of energy in a high-starch format relative to need.

Dietary Considerations for ER

The amount of energy fed and the type of energy fed are important considerations whether looking to avoid an acute feed-related episode or considering the management of a horse with the recurrent form.

Other nutrients often talked about when managing ER include vitamin E, selenium and electrolytes. Historically the inclusion of vitamin E and selenium were considered important for the prevention of further episodes; however, there is no evidence to support such use. A case of deficiency in either of these nutrients may well put the horse at a disadvantage and could perhaps create a state where occurrence is more notable; however, with the advent of fortified and balanced complete bagged feeds, such nutrients are normally supplied in more than adequate amounts. Their role as antioxidants, which function to “mop-up” damaging free radicals generated through training, is where their use can benefit any horse at this level of work. The use of additional vitamin E is also recommended when increasing the fat content of the diet—a common practice when feeding horses with recurrent ER.

Electrolytes do play an important role in normal muscle function, and any deficiency noted in the diet should be corrected. Identifying a need in the diet is more easily done than determining if the individual horse has a problem with absorption or utilisation of the electrolytes. A urinary fractional excretion test (FE) will highlight issues, and subsequent correction through the diet to return the horse to within normal ranges may offer some improvement. However, it is important to note that for horses with recurrent ER, where an intrinsic muscle defect is present, the research to date has shown no electrolyte imbalances or differences between such horses and unaffected horses.

Quantifying “Low-Starch and High-Fat” Feeding

The recommended practice for management of ER is a reduction in starch and an increase in fats. This practice has two ways of benefiting the horse: a reduction in “spookiness” or reactivity and a positive effect on muscle damage as seen by lower CK (creatine kinase) levels following exercise.

Positive effects on lowering CK levels were found when a higher proportion of the energy fed came from diets higher in fats and lower in non-structural carbohydrates (starches and sugars). The effect was noted when fed at 4.5kg/day—an amount easily reached and normally surpassed when feeding horses in training. The beneficial diet provided 20% of energy from fats and only 9% from starches and sugars, compared to the more traditional sweet feed diet providing 45% of energy from starches and sugars and less than 5% from fats.

Finding Fats

Top dressing of oils will increase fat in the diet—with a normal intake of up to 100 mls per day. Although the horse can digest higher amounts, palatability usually restricts a higher intake. Pelleted or extruded fat sources are increasingly popular as alternatives to oils for their convenience of feeding and palatability. Straight rice bran and blends of materials such as rice bran, linseed and soya are available from most major feed companies. Oil content will typically range from 18-26% providing 180g-260g of oil per kilogram as fed.  

Racing feeds will also provide oil in the diet; content is quite varied, typically from 4-10% providing 40g-100g per kilogram as fed. Hay and haylage also contains oil at a low level, typically 2% providing just 20g per kilogram on a dry matter basis.

Choosing Carbohydrates

Traditional feeding based on oats and other whole grains will have a higher starch content than feeds using a combination of grains and fiber. Levels of starch found in complete feeds and straights have a broad range from as low as 8% in a complete feed—specifically formulated to have a low-starch content—and up to in excess of 50% for straights such as barley and naked oats.

TO READ MORE —

BUY THIS ISSUE IN PRINT OR DOWNLOAD -

Triple Crown 2019, issue 52 (PRINT)

$6.95

Triple Crown 2019, issue 52 (DOWNLOAD)

$3.99

WHY NOT SUBSCRIBE?

DON'T MISS OUT AND SUBSCRIBE TO RECEIVE THE NEXT FOUR ISSUES!

Print & Online Subscription

From $24.95