INDUCTION OF OVULATION IN THE MARE WITH THE SYNTHETIC GNRH ANALOG LEUPROLIDE

A study was performed to evaluate the efficacy of the synthetic GnRH a nalogue leuprolide (Lupron(TM):Tapp Pharmaceuticals, Inc., Chicago, IL ), far the induction of ovulation in the mare. Sixty mares (registered Arabian, Paint, Quarter Horse and Tennessee Walking) were utilized. T reatment consisted of two 15-mg SC injections, 24 hours apart, beginni ng when the first preovulatory size follicle was detected. Mean durati on of estrus was also longer in the control group (control 10.5 vs. tr eated 5.6 days, P < 0.005). The mean interval from detection of the pr eovulatory size follicle to ovulation was longer in control vs. treate d mares (7.9 vs. 1.8 days, P < 0.0001). Time between ovulation and the end of estrus, size of the largest follicle on the first day of estru s, and the day of estrus when the pre-ovulatory follicle was first det ected were not different between the control and treatment groups. Mea n follicle size at first injection was 37 mm (range 28 to 48 mm). Mean preovulatory follicle size (mm) within 24 hours of ovulation was smal ler during treatment (39.1) than during control estrus (42.0, P < 0.05 ). Pregnancy rate was not different after either one (80.9%) or two br eedings (84.6%) during the treatment estrus. This study showed that th e GnRH analog leuprolide (Lupron) can be easily and effectively utiliz ed for induction of ovulation in the mare.