Induction of parturition in the bitch with the progesterone-receptor blocker aglépristone.

The triggering mechanism for parturition in the bitch remains unclear. Consequently, the development of drugs to successfully induce parturition in the dog has been difficult. The aim of this study was to evaluate the efficacy of the progesterone-receptor blocker aglépristone for the induction of parturition in beagle bitches. The course of parturition was therefore investigated in six parturitions induced by aglépristone and in six spontaneous parturitions. In addition, data were collected on pup survival and growth rates. Aglépristone was administered twice with a 9h interval on day 58 of pregnancy. If parturition did not proceed a standard intervention protocol was applied. Expulsion of the first pup occurred between 32 and 56 h after the first treatment with aglépristone, at which time the plasma progesterone concentration was still elevated. Accordingly, the gestation length of the bitches in the induced group (59.5+/-0.2 days) was significantly shorter than that of the spontaneously whelping bitches (62.2+/-0.5 days). The expulsion phase length, the inter-pup interval, the number of puppies born dead, and the number of clinical interventions needed during parturition did not significantly differ between the spontaneously whelping and the induced group. Pup survival and mean birth weights in the two groups did not differ significantly and aglépristone treatment had no significant influence on the growth rates. The results of this study show that aglépristone is an effective drug which can be used safely for the induction of parturition in the dog.