In recent years, gastric ulceration has been recognised as a common, possibly performance-limiting disease of adult horses. Here, we aim to provide the reader with a useful review of recent literature covering all aspects of equine gastric ulcer syndrome (EGUS) in adult horses. The anatomy and physiology of the stomach, with particular reference to secretion of acid and mucosal protective mechanisms, are reviewed, as are the differing theories relating to the aetiopathogenesis of gastric ulceration. We also explore the possible influence of various management factors on development of the disease. The prevalence of the disease in racehorses has been reported to be as high as 100%. In general, horses that are in active training for racing tend to have a prevalence of around 90%, whereas pleasure horses in full work have a reported prevalence of approximately 60%. Emerging diagnostic tests which could obviate the need for gastroscopy are introduced and current recommendations for treatment are summarised, focussing on proton pump inhibitors, in particular omeprazole, administered orally. The oral administration of omeprazole has been shown to be effective in both treating horses with gastric ulceration and at preventing re-occurrence whilst the horses are in training, provided that daily dosing is maintained.

The prevalence of gastric ulceration in racehorses in New Zealand is similar to that reported elsewhere for horses in active training for racing. Access to pasture for some or all of the day did not appear to be protective.

SummaryReasons for performing study: This study investigated the physiology of endurance horses competing in warm weather over technical terrain, a situation where horses may become metabolically compromised. Hypotheses: There will be changes in physiological, haematological and biochemical variables as horses progress through the 160 km ride and horses detected clinically at the veterinary inspections as metabolically compromised will have significant differences in measured laboratory variables compared to horses that complete the ride successfully. Methods: Forty-eight horses competing in the Australian TomQuilty 160 km endurance ride were monitored and weighed, and blood samples collected for analysis of electrolytes, packed cell volume (PCV), plasma protein and acid-base variables, preride, mid-ride, at the end of their ride and the following morning after a period of recovery. Statistical analysis was performed using multinomial logistic regression and repeated measures ANOVA. Results: Of the 48 horses participating in the study, only 18 successfully completed the ride (SC), 16 were eliminated for lameness (VOL) and 10 for metabolic reasons (VOM); 4 were voluntarily withdrawn by the riders. A lighter preride bodyweight was predictive for VOM. PCV and total plasma protein increased mid-ride in all groups compared to preride, with significantly greater increases in PCV for VOM compared to the other horses. Changes were detected in blood concentrations of sodium, chloride and calcium over time and between the groups, with lower mid-ride sodium and chloride in VOM compared to SC and VOL. Conclusions: VOM horses weighed less preride and were, on analysis of blood and physiological variables mid-ride, more dehydrated with greater electrolyte depletion than the SC or VOL horses. evj_225 6..11

Rate and ionic composition of sweat fluid losses and partitioning of evaporative heat loss into respiratory and cutaneous components were determined in six horses during three 15-km phases of exercise at approximately 40% of maximal O2 uptake. Pattern of change in sweat rate (SR) and composition was similar during each phase. SR increased rapidly for the first 20 min of exercise but remained at approximately 24-28 ml . m-2 . min-1 during the remainder of each phase. Similarly, the concentrations of Na and Cl in sweat increased until 30 min of exercise but were unchanged thereafter. Sweat osmolality and concentrations of Na and Cl were positively correlated with SR. Sweat K concentration decreased during exercise but was not correlated with SR. Fluid losses were 33.8 +/- 1.5 liters, resulting in decreases of approximately 21% in plasma volume and approximately 11% in total body water. The approximately 6% hypohydration was not associated with an alteration in SR, sweat composition, or heat storage. Respiratory and cutaneous evaporative heat loss represented approximately 23 and 70%, respectively, of the total heat dissipated, and the partitioning of heat loss was similar in each exercise phase. We conclude that SR and the relative proportions of respiratory and cutaneous evaporative heat loss are unchanged in horses during prolonged low-intensity exercise despite moderate hypohydration.

Intravenous infusion of formaldehyde at doses that do not induce adverse reactions did not have a detectable effect on measured hemostatic variables in healthy horses.