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

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. 

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.

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