Written By Dr. Kris Hiney
The last article briefly discussed the horse’s gastrointestinal system and the challenge it presents to feeding management. This month we will discuss a specific disorder, equine gastric ulcer syndrome. Just like us, horses can suffer from painful gastric ulcers which can lower their performance ability, and certainly their overall health and well being. Due to their unique physiology they may be even more susceptible to ulcers than other domestic animals. Symptoms of ulcers include decreased feed intake, lowered performance, a rough hair coat, laying down excessively or even grinding their teeth.
GI Tract Again
When wondering why horses seem to be so prone to ulcers, it is important to really think about what their digestive anatomy is designed to do. In the stomach of the equine, there are two regions, a glandular region which secretes hydrochloric acid and digestive enzymes, and a non-glandular region in the upper or proximal part of the horse’s stomach. The mucosal cells of the horses glandular portion are well suited to protect against the acids that would normally be present in the horse’s stomach. However, the cells in the non-glandular region are not as protective, and repeated exposure to digestive acids can result in creation of lesions in the stomach. Now normally, this is not a large problem for the grazing horse. When a horse is eating continually, they will be constantly producing saliva with buffers that serve to increase the pH in the horse’s stomach, and prevent any damage to the mucosa. When horses are not eating, no saliva enters the stomach, and the pH begins to drop. This can occur within 5-6 post eating. As stated last month, if your horse remains without feed for 10 hours, his stomach will be completely empty, and the pH drops even lower. Foals are especially susceptible, and any foal that goes off feed due to illness may end up with a secondary problem of ulcers. Look for your foal to be grinding their teeth or lying on their back. These are classic signs of ulcers in foals.
Is Grain the Problem?We also see an increase in ulcer prevalence in horses that are on high grain diets. Now this may actually be due to a combination of factors, which we will see soon. But high concentrate feeding itself can be a culprit. When horse’s are fed concentrates, either in the form of pelleted or whole grains, the amount of time a horse will relatively spend consuming that feed will be less than that on long stem forage. It simply takes less “chews” to eat a pound of grain vs a pound of hay. Less chews equal less saliva production as well as a longer interval between the next feeding (ie he finishes faster). In addition, concentrates themselves cause production of a different type of volatile fatty acid production in the stomach. While the hind gut was long considered the sole domain of fermenting bacteria in the equine, we now know that isn’t true. Microbes do indeed exist in the stomach of the horse, and some types will flourish on a higher grain diet. This particular bacteria result in production of more acidic waste products, which further decrease your horse’s stomach pH.
What Else is Going Wrong?As I said earlier, it may be incorrect to point the finger solely at feeding horses high amounts of concentrates. After all, what types of horses consume large amounts of concentrate? Hopefully you remember from our earlier series which types of horses need high amounts of Mcals. These are typically heavily working performance horses that need the grain in the diet to meet their caloric needs. But what else is unique about these guys? One, they are exercising more, which in itself may help contribute to the problem. When horses are galloping, the abdominal contents of the horse are essentially “squished” forward as the hind legs reach up under the horse prior to the forelegs reaching back forward. This forces the more acidic contents of the glandular portion of the horse’s stomach up into the less well-protected non-glandular region.Secondly, performance horses are frequently stalled individually. It is simply a fact of the matter that these horses must be kept blemish free and protected from too much rough play with others. Some horses even have an aptitude to hurt themselves when playing on their own too vigorously. However, stalling can be a source of mental stress for horses, as it eliminates their natural tendency for continual movement throughout the day, as well as their foraging behavior. It also removes the horse from its natural desire to be a herd animal. Horses in the wild are never seen in isolation, unless they are sick or injured. Therefore, isolation can be extremely stressful for some horses.
Another leading cause of ulcers is the use of non-steroidal anti-inflammatory drugs or NSAIDS. These drugs block an enzyme necessary in the pathway that produces prostaglandins that cause inflammation. However, as these drugs are not specific for blocking production of only one type of prostaglandin, they also block formation of the prostaglandins which help maintain gastric mucosal integrity and are anti-inflammatory. Therefore, long term use of NSAIDS can almost certainly cause ulcers in horses, and is typically avoided unless necessary. However, the rigors of training and exercise may cause theses horses to be provided NSAIDS more frequently than horses in only light or recreational riding.
Even the career of your horse may be stressful. Racehorses have a much higher incidence of ulcers than other types of performance horses, but again this could be attributed to many factors: high concentrate diets, stalling, exercise etc. Even transport has been reported as ulcer inducing. In a group of thoroughbreds, transport for 6 hours was reported to increase the prevalence of lesions in the stomach, however this was not observed in western performance horses. I would propose that simply the personality of the horse plays a large role. Is your horse a fretter and a worrier or one that could happily march through a parade without batting an eye? After all, ulcers are more common in us type A individuals than our more laidback neighbors!
One of the easiest ways to control the incidence of ulcers in horses is to alter our management strategies. Feeding horses at more frequent intervals, or providing meals of long stem forage at an amount to prevent an absence of feed availability is ideal. That may mean spreading out the feeding interval to 12 hours or by providing your horse with a larger evening meal to last closer to breakfast. Also consider the type of feed you are using. Long stem forage will cause a horse to chew for a longer period of time, compared to pelleted rations. Horses that are on complete feed are especially more likely to be “out of feed” for a longer period of time unless your horse is a committed nibbler. Even horses on complete feeds due to loss of teeth can benefit with the offering of hay to munch on in between feedings.We can also try to decrease the stress level of horses, which may be easier said than done. After all, what is stressful for one individual may not be for another. Look for behavioral signs that let you know your horse needs more turnout time or more social contact. Try to reduce the stress of trailering by making sure your horse is trained to load easily and travel quietly. Make sure you are not a stressful driver either, taking corners too sharp or braking too suddenly!
There is also some limited research that suggests that the type of hay fed to horses may alter the incidence of ulcers. Horses on an alfalfa based diet relative to a grass hay diet appear to have lower incidence of ulcers. It is unknown whether this may be due to the protein or calcium content of the hay.
Alternative to NSAIDS
Much research in both humans and horses has been aimed at dietary interventions to prevent inflammation. The use of omega-3 fatty acids has been repeatedly shown to decrease inflammation in humans, and has had some promising use in horses as well. Addition of omega-3 fatty acids in the diet helps to block production of arachidonic acid, which is a producer of inflammatory thromboxanes, prostaglandins etc. Thus, use of adequate levels of omega-3 fatty acids in the diet may lessen the need for use of NSAIDS as therapy in the performance horse. In addition, polyunsaturated fatty acids may be able to help protect against gastric ulcers. In rats given dexamethasone to induce ulceration, a diet high in PUFA helped to suppress ulcers and maintained the normal lipid bilayer in the gastric mucosa. Furthermore, addition of omega 3 fatty acids may lower the stress experienced by horses as measured by cortisol production (a hormone related to stress). In mares provided with an omega-3 fatty acid source, cortisol levels were lower than controls following a period of stall confinement used to induce stress. Thus, while not proven to be a direct preventative of ulcer formation in horses, there is much promising data to indicate the effectiveness of omega 3 fatty acids as a dietary aid.
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