Phenylbutazone treatment in breeding stallions: Preliminary evidence for no effect on semen or testicular size

Effects of phenylbutazone treatment on semen and testicular size were evaluated using 6 mature stallions. Three stallions were given 1 g phenylbutazone orally in feed twice daily for 4 weeks, and 3 stallions remained untreated. Semen samples were obtained daily for 7 consecutive days once during a 2-week baseline period (Week 2), once after 4 weeks of treatment (Week 6), and once following 1 complete spermatogenic cycle (60 days) after treatment was discontinued (Week 16). During the remaining weeks (Weeks 1,3,4,5,7,8 and 9), semen was collected twice weekly. Semen samples were evaluated using traditional and computer-assisted techniques at the time of collection and at 24 and 48 hours of storage at 4°C. Testicular volume was estimated using ultrasonography once during each period of the study. Repeated measures analysis of variance revealed no significant measurable effects of phenylbutazone treatment on semen at the time of collection or after storage at 4°C for 24 or 48 hours. Similarly, no effect on testicular volume was found.