Comparison of induction of oestrus in dogs using metergoline, metergoline plus human chorionic gonadotrophin, or pregnant mares' serum gonadotrophin.

Twenty beagle bitches were treated with metergoline (groups I and II), ten with pregnant mares' serum gonadotrophin (PMSG; group III) and ten served as an untreated control group. Metergoline (12.5 mg per bitch) was injected intramuscularly (i.m.) every 3 days, starting between days 78 and 161 after the previous pro-oestrus. In 18 of the metergoline-treated bitches the interpro-oestrous interval (144 +/- 29 days) was significantly shorter (P < 0.01) than that of the control group (206.7 +/- 29.7 days). Of these 18 responder bitches, ten had not received human chorionic gonadotrophin (hCG) whereas eight had received 500 iu hCG i.m. in late pro-oestrus (group II). The durations of pro-oestrus and oestrus of the ten responding bitches not given hCG (6.8 +/- 5.5 and 11.7 +/- 4.5 days, respectively) did not differ (P > 0.05) from those of the control group (7.8 +/- 3.6 and 11.2 +/- 3.2 days). All ten bitches ovulated and nine became pregnant. Two of eight bitches responding to metergoline in group II exhibited a prolonged pro-oestrus after injection of hCG. In the remaining six bitches, the average duration of pro-oestrus and oestrus was 4.8 +/- 1.7 and 6.5 +/- 2.8 days, respectively, which was significantly shorter (P < 0.05) than in bitches not given hCG. The incidences of ovulation (6/8) and gestation (4/8) were lower than in bitches that received metergoline alone, or in the control group.(ABSTRACT TRUNCATED AT 250 WORDS)