†California Veterinary Diagnostic Laboratory Service, California 95616, California 91024, USA. Summary Although gastric ulcers have been identified relatively frequently in racing Thoroughbreds, there have been no large scale studies to determine their effect on health and performance. Two hundred and two Thoroughbred horses in active race training were selected by the attending veterinarians for gastro‐endoscopic examination. Images of the stomach mucosa were stored in a digitised format for subsequent evaluation. The number of ulcers and a score of severity were determined. Gastric ulceration of the squamous mucosa was identified in 82% of horses. Seventy‐three (39%) horses displayed clinical signs consistent with gastric ulceration. Increasing Furr and Murray Score was associated with poor hair coat (P = 0.03), colic (P = 0.03), and increasing serum creatinine concentration (P = 0.029). There were no associations between haematology and serum biochemistry values (other than serum alkaline phosphatase concentration and serum creatinine concentration) and gastric ulceration. Our study confirmed the relatively high incidence of gastric ulceration in Thoroughbred horses involved in active race training. Gastric ulceration is a potential, but rare, cause of overt colic, but may produce more subtle detrimental effects on a horse's condition. It is concluded that the diagnosis of gastric ulceration should be based on an endoscopic examination of the stomach, although future studies are required to elucidate further the aetiology and clinical significance of gastric ulceration.

Regional differences in responses to erythromycin, lidocaine, and metoclopramide were evident in the gastrointestinal tract of horses. Metoclopramide increased CA in all tissues used, whereas erythromycin inhibited CA in circular smooth muscle but stimulated CA in longitudinal smooth muscle from the PA. Inhibition is caused by stimulation of inhibitory nerves and is mediated, in part, by nitric oxide and vasoactive intestinal peptide.

Summary Sixty‐seven foals age <150 days underwent a ventral celiotomy for colic. Of the 67 foals, 51 foals (82%) recovered from anaesthesia and 42 (63%) were subsequently released from the hospital. Three (6%) of the 51 foals were subjected to a repeat celiotomy. Long term follow‐up was available on 36 foals. Twenty‐nine (57%) of the 51 foals recovered from anaesthesia, were alive at least 2 years following surgery. Adhesions were identified in 8 (17%) of the foals which recovered from general anaesthesia but were subsequently subjected to euthanasia due to recurrent colic. Strangulating lesions were associated with a lower survival rate. Nineteen per cent of foals with strangulating intestinal lesions survived >2 years following surgery, compared to 69% of foals with nonstrangulating lesions. The age of foals on admission had a significant effect on survival. Only 10% of foals less than 14 days of age survived, compared to 45.8% of foals between age 15 and 150 days.

Summary A multicentre, blinded, randomised complete‐block, field trial was conducted with 140 horses and foals age 4 weeks‐28 years to determine if omeprazole paste is effective and safe in promoting healing of spontaneous gastric ulcers under a variety of field conditions and in different breeds and ages of horses. Horses in the study had gastric ulceration as determined by gastroscopy and were divided into replicates of 4 or 5 animals. One horse in each replicate was assigned randomly to receive an empty omeprazole syringe (sham‐dosed control) and the remaining horses received omeprazole paste once daily for 28 days. Gastroscopy was repeated at the end of the study. Horses treated with omeprazole had significantly (P<0.01) more improvement in ulcer scores at the end of the study compared with controls. Ulcers were improved in 32.4 and 99.0% of the control and omeprazole groups, respectively. Ulcers were completely healed in 8.9 and 86.7% of the control and omeprazole groups, respectively. Under typical field conditions, omeprazole was effective at enhancing healing of spontaneous gastric ulcers in horses of a variety of ages and breeds.