Domestication of the horse and why we find ulcers

Quite common. Studies investigating the occurrence in performance horses found that 70-100% of performance horses are affected with gastric ulcers, with lower occurrence rates outside the training and competition season. Studies of pleasure horses in not much work found 11-55% affected. The majority of studies has been done on performance horses, presumably because it is more efficient for researchers to ‘collect’ many horses to evaluate on larger/professional yards, and the decision for an owner/trainer to invest in gastroscopy might be made sooner expecting a financial return if the horse is not performing as expected. 

If we think back about the evolution of the horse, the horse and its predecessors are ‘designed’ to walk many miles each day, nearly continuously grazing in their herd. Initially ‘eohippus’ evolved 50 million years ago to live in the rainforest, and then evolution brought the horse to be a grazer of plains initially in North America, where the available land would have provided stalky forage with low starch and sugar content. As the natural habitat changed to plains and steppes, the horse became more athletic to outrun predators. Around 6000 years ago (so quite recent in the scale of things!) the horse became domesticated. Their athleticism was useful to humans, and this became a selectable ‘trait’ in the further evolution of the horse. Modern horses, all of them from the Thoroughbred to a Shetland pony are athletes if we compare them to their predecessors. Their activity level has changed from walking/grazing all day long to now high-intensity exercise for a short period per day. To keep up with the calorie requirements for this higher-level exercise, we do also feed performance horses with grains and other high starch/high calorie feeds.

Before domestication, evolution would not be biased against development of ulcers because the ancient horse did not have as many reasons to develop ulcers. Also, ulcers are very rarely lethal, so during the early domestication of the horse the selection in evolution would not have been biased against horses who were developing ulcers. 

Not only has the horse developed over the years, but so have vets and their equipment. The development of gastroscopes is relatively recent in the scale of things, and that is why research papers investigating gastric ulcers have started to come out in the last few decades. Before that, ulcers did occur, but they would only have been found in abattoir studies and not in living horses.

The ‘talk’ about gastric ulcers in horses has developed not because our management has worsened or that they have recently developed in horses, it is simply because we now have the ability to find them.

Some critics would say this. We disagree. Horses are athletes, and especially the top athletes have a job to do. It is not feasible to ‘return all horses to nature’, nor would the modern horse be able to cope with that in any way. For UK pleasure horses in not much work, the occurrence of obesity and laminitis is high, and the relevance to the individual is quite likely higher than the development of minor gastric ulcers. The modern horse does need exercise, and in many ways relies on their domesticated nature and the management and care that comes with it. Within those parameters, there are improvements of general management that can be made. Most horse owners/trainers already implement these strategies. They are described further down on this page.