Induction of ovarian activity in anoestrous beagle bitches

Abstract This study was performed on 24 anoestrous beagle bitches. Four were untreated and served as controls. Ten late anoestrous (group A) and ten mid-anoestrous (groups B and C) animals were treated daily with 500 i.u. PMSG i.m. for 10 days. Group A and B (n = 5) females received a 500 i.u. injection of HCG i.m. and group C (n = 5) were injected with 50 μg gonadoliberine (GnRH) on day 10. Clinical signs of proestrus and oestrus were recorded daily and plasma progesterone was assayed from blood samples collected on days −3, 4, 8, and 10 (day 0=first injection of PMSG). All bitches were seen in proestrus, the mean starting day being day 6. Nine females in group A, four in group B and three in group C accepted mating but the mean duration of oestrus was only three days. Only three bitches, from group A, conceived (15 pups). The progesterone patterns showed a dramatic increase as early as day 4 and the mean levels were excessively high on day 10, i.e. prior to oestrus when displayed (19 ng/ml in group A, 8 ng/ml in group B and 7 ng/ml in group C). The treatments induced proestrus but the duration of oestrus and the progesterone concentrations during this phase seemed abnormal and may be related to the low fertility achieved. Better oestrus and ovulation control is still required before routine use of such treatments are recommended.