Simple SummaryStomach ulcers are common in horses. They cause pain and are a serious welfare problem. Several risk factors have been identified and stomach ulcers are routinely treated with omeprazole, a drug that reduces stomach acid secretion. Fourteen mares with severe stomach ulcers, previously used as embryo recipients, were studied. The horses were kept in individual stalls, exercised in a horse walker once a day and fed ad libitum hay and a small amount of low starch hard feed. Half of the horses were also fed a supplement containing hydrolysed collagen. After 4 weeks, the severity of the ulcers had decreased in both groups and ulcers had healed in 7 out of 14 horses. There was no difference between the horses that had received the supplement and those that had not. Severe stomach ulcers can improve, and even heal, with a diet of ad libitum forage, without the use of omeprazole. A predictable daily routine, with a limited number of dedicated caretakers, may have contributed to the improvement of gastric health.AbstractEquine squamous gastric disease (ESGD) is common in horses and poses a serious welfare problem. Several risk factors have been identified and ESGD is routinely treated with omeprazole. Fourteen mares, previously used as embryo recipients and diagnosed with ESGD, were selected. Horses were confined to individual stalls, exercised once daily, and fed ad libitum hay, 1 kg of a low starch compound complementary feed and a mineral supplement. Half of the horses received a compound containing hydrolysed collagen (supplement) and the other half did not (control). At the start of the study, ESGD scores were 3.57 and 3.36 for the supplement and control group, respectively. After 4 weeks, the ESGD grades were significantly reduced in both groups (1.89 and 1.43, respectively,p< 0.01), and healing (ESGD < 2) occurred in 7 out of 14 horses. No treatment effect was observed (p= 0.75), and it was concluded that the change in husbandry overshadowed any potential effect of the compound. Severe ESGD can improve, and even heal, with the provision of a diet of ad libitum forage and a small amount of a compound complementary feed, without the use of omeprazole. A predictable daily routine, with a limited number of dedicated caretakers, may have contributed to the improvement of gastric health.