Equine gastric ulcer syndrome in New Zealand racehorses : a thesis presented in partial fulfilment of the requirements for the degree of Master of Veterinary Science at Massey University, Palmerston North, New Zealand

Aims To establish the prevalence of gastric ulcers in New Zealand racehorses. Methods A prevalence study was conducted during 2003 and 2004 in New Zealand. One hundred and seventy one horses from 24 trainers across New Zealand were examined with gastroscopy as part of the study. Images of the examination were recorded and reviewed. The stomachs were assigned an ordinal score based on the severity of the gastric ulceration present. Results There were 171 horses in the study: 133 Thoroughbreds and 38 Standardbreds. One hundred and fifty one (88.3%) of these had evidence of EGUS. There was no significant difference in the prevalence of ulceration between the two breeds (p=0.51) or between horses of differing ages (p=0.56). There were 141 horses kept at pasture for at least four hours per day, of these 125 (89%) had EGUS. Thirteen horses were kept at pasture full time and all of these had EGUS. Seventeen horses were stabled full time and 16 (94.1%) of these had EGUS. There was no significant difference between the different housing groups and the prevalence or severity of EGUS (p=0.33 and 0.13 respectively), and there was no significant difference in the severity of gastric ulceration (p=0.12) between the horses grazed on different pasture qualities. There was no significant difference in the prevalence (p=0.26) or severity (p=0.49) of gastric ulceration based on the duration of training. Conclusions The prevalence of EGUS in New Zealand racehorses is similar to that reported elsewhere for horses in active race training. The type of turnout that these horses receive does not appear to be protective for EGUS. Clinical relevance Pasture turnout alone may not be protective against EGUS in racehorses that are in active training. Gastric ulceration is a common problem in New Zealand racehorses and may be a cause of decreased performance in these animals