Administration of sulpiride or domperidone for advancing the first ovulation in deep anestrous mares

Since results with using sulpiride and domperidone are conflicting and since both have not been tested at the same time, the aim of this study was to compare the efficacy of these substances for the induction of ovulation in deep anestrous mares in the same experimental conditions and to determine their fertility after artificial insemination (AI) at the induced estrus. Twenty-six non-pregnant, non-lactating standardbred anestrous mares were randomly assigned to three groups and treated daily for 25 days (from February 3rd to February 28th) with either sulpiride (1 mg/kg of body weight im SID, n = 10), or domperidone (1 mg/kg po SID, n = 10); 6 animals were used as control. The beginning of the transition period and the first ovulation were hastened in sulpiride (16.4 ± 0.8 days) but not in domperidone (46.0 ± 3.3 days) treated mares (P < 0.05). The diameter of the largest follicle was affected by treatment, time and interaction of treatment-by-day (P < 0.05) and significantly increased in the sulpiride group (P < 0.05). Although a main effect of treatment on plasma LH concentration was not observed (P = 0.06), time and interaction of treatment-by-day were statistically significant (P < 0.05). The interval from the beginning of treatment to first ovulation was shorter (P < 0.05) in the sulpiride group (36.9 ± 2.5 days) than in the domperidone (74.7 ± 3.3 days) and control (81.4 ± 3.1) groups. The establishment of pregnancy was significantly (P < 0.05) hastened in sulpiride (61.0 ± 35.2 days) but not in domperidone (83.0 ± 44.0 days) treated mares. Treated mares not pregnant after the first AI, showed normal estrous cycles with regular interovulatory intervals (P > 0.05). It was concluded that sulpiride is effective in advancing the beginning of transition period and the first ovulation whereas domperidone is successful only in some mares.