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

By Catherine Rudenko

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

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

Clarifying Gastric Ulceration

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

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

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

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

Risk Factors

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

• Pasture turnout

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

• Choice of alfalfa over other forages

• Provision of straw as the only forage source

• Restricted access to water

• Exceeding 2g of starch per kilogram of body weight

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

• Frequency and intensity of exercise

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

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

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

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How the digestion of nutrients may improve horses’ overall condition

By John Hunter

The importance of breeding and training are well established, but there are many differences in the way yards prepare their horses. For several years our group—a trainer, a vet, and a physician specialising in nutrition and the gut—have been working to see if we could improve equine health and performance using a scientific approach.

The aim has been to explore ways in which the biochemistry underlying the digestion of nutrients might improve horses’ overall condition. In some cases this involved applying developments in the field of human nutrition to horses.  In others we have tackled well-established problems within equine physiology. 

Beetroot juice supplementation

Beetroot is a rich source of nitrate and is frequently taken by athletes to improve their performance. Nitrate produces nitric oxide, which dilates blood vessels, thus reducing blood pressure, increasing blood supply and promoting glucose absorption, and potentially increasing the energy available for high-speed exertion. However, not all athletes appear to benefit, and there had been no study so far on the effect of beetroot juice in horses.  

Twenty racehorses (colts and geldings) in full training were divided into two groups. All were fed their standard diets. One group received beetroot juice with a sweetener to mask the taste and the other a sweetener only for four weeks. After four weeks, nitrate levels in the blood were measured and compared to the starting levels. The level of nitrate rose very slightly in the test group, but no change in performance or condition was noted in any of the horses. Beetroot juice does not seem to help horses.

Vitamin B12

Vitamin B12 is important, not only for preventing anaemia and maintaining the health of the nervous system, but also because it produces enzymes which are crucial for allowing the entry of nutrients into the biochemical cycles producing the main source of energy in both man and horse: ATP. In humans, B12 is derived from eating meat, fish and dairy products. Horses and other herbivores, obtain their vitamin B12 by ingestion of cobalt from pasture which is then used by intestinal microorganisms to form the vitamin. As racehorses are rarely turned out on pasture, most feed concentrates are supplemented with B12.

‘As the intensity of work increases, the composition of the diet and the amount of food consumed change as a consequence of the increased consumption of starchy cereal grains. This will alter not only the dietary supply of B vitamins but also the intestinal synthesis…and it is an open question whether the rate of their absorption is exceeded by tissue demand when horses are in intensive training’ (Frape 2010, p250).

The amount of soluble carbohydrate in the diet of the racehorse must be carefully regulated. ‘Racehorses on a high-concentrate/low-roughage diet and little access to grazing are to some degree already on a metabolic knife-edge’ (Ramzan, 2014, p258).

The trainer was concerned that a number of horses in his yard were below par from the start of the Flat season as their appearance and performance were disappointing. Their diet was unchanged, but they ate poorly and failed to regain weight after racing. Veterinary investigations, including full blood screening, failed to reveal any cause.

As lethargy and early fatigue are two of the earliest symptoms of B12 deficiency in man, it was decided also to check the B12 status of the horses affected. Twenty racehorses, which were out of condition, were identified and divided into two groups. Blood samples were taken, and B12 levels were recorded.  One group was supplemented with B12 injections at 3mg twice weekly for three weeks (18mg in total). The other group acted as controls. At the end of that time, the horses’ condition was reassessed by the trainer on his return from a week’s absence.

The concentration of vitamin B12 in the 20 horses was found to lie within the normal range and was slightly greater than that found in healthy yearlings on pasture at a local stud. After B12 injections, the level rose significantly. A further determination later in the season showed that this initial increase had disappeared. Overall there was no difference between the blood levels of B12 at the end of season compared to the beginning. Changes in B12 concentration, however, did not affect performance. The trainer, who was not informed which horses had received B12 supplements, considered that 8 horses had improved and 12 had not. These were equally distributed between the two treatment groups, and those considered to have improved did not have higher levels of B12.

Thus, despite previous anxieties, racehorses on standard diets have normal B12 levels which remain satisfactory throughout the season. Supplementary injections increase blood concentrations temporarily, but there was no correlation between blood B12 concentration and performance.

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