Behavior of Horses With, Without Gastric Ulcers Compared

Think of all the horses you know fairly well. You know how they eat, how they act, how they perform. Now, among those horses, can you pick out the ones with gastric ulcers?

According to Danish equitation scientists, unless you run some investigative exams such as a gastroscopy (an endoscopic examination of the stomach), recognizing an “ulcerated” horse by observation alone might not be as easy a task as previously thought. And that’s true for riders, grooms, breeders–and even veterinarians. Because after a study involving nearly 100 sport horses in a private Danish stud, it became clear that “ulcerated” horses didn’t seem to look or act significantly different from healthy horses, and there was almost no difference in their eating habits.

“There was surprisingly little difference between groups of horses with and without severe gastric ulceration from the same stable, fed equal amounts of starches and hay,” said Jens Malmkvist, PhD, researcher in the animal science department of Aarhus University in Tjele, during his presentation at the 2011 International Society for Equitation Science (ISES) Conference, held Oct. 26-29 in Hooge Mierde, The Netherlands. “All horses were in good body condition and crib-biting was rarely observed.” Specifically, researchers observed only one horse in the entire study (an ulcerated horse) cribbing, he said.

Malmkvist and colleagues examined 98 study horses via gastroscopy of both the upper and lower (glandular) areas of the stomach. Thirty-three of these horses were found to have at least one “severe gastric ulcer lesion” (scoring 3 or 4 out of a maximum 4), and 30 of them had at least one lesion in the glandular area.

The 30 horses with ulcers in the lower portion of their stomach were then compared to another 30 determined through gastroscopy to have healthy upper and lower gastric mucosa. Malmkvist studied the horses’ heart rates and the cortisol (“stress hormone”) levels in their droppings before and after showing them a new object (to evaluate how they react to a stressful situation). He also fed the horses a “teaser” amount of food instead of their full meal the day after the new object test, as this would make stereotypic horses (those with bad habits such as cribbing and windsucking) more likely to show their behavior, he said. The horses were given their full meals an hour later.

Upon reviewing the results of the study (which won the “Most Promising Research Presented at ISES 2011” award at the conference), Malmkvist found the ulcerated horses had a tendency to eat a little bit faster when their dinner was late. “This may indicate that ulcerated horses are more motivated to eat when deprived of food,” he said. They also showed laboratory signs that suggest ulcerated horses are more sensitive to acute stress.

However, he noted, “The ulcerated horses were not more fearful, and they didn’t show any more negative behavior than the healthy horses. But they did have a higher endocrine response after the novel-object test, and that could mean that they are more sensitive to acute stress.”

So although an ulcerated horse might look and act just fine, he might actually be masking pain caused by gastric ulcers, Malmkvist said. Consequently, he highlighted the importance of having horses suspected of having ulcers undergo a gastroscopic examination to visually check for ulcers.

He added that it’s crucial for the veterinarian to check both the upper and lower regions of the stomach, as the lower region appeared the most common place for ulcers to develop in the current study: “Our study indicates that we should also consider glandular gastric ulceration, as this part was, in contrast to the expectation, the most damaged area in the horses studied,” Malmkvist concluded.