Shortening of the interoestrous interval and the lifespan of the corpus luteum of the cyclic dog by bromocryptine treatment

Abstract

Four beagle bitches were treated orally, twice daily with 250 micrograms bromocryptine, an inhibitor of prolactin secretion, from D1-D5 (D1 is defined as the first day of the luteal period) until the onset of the next prooestrus (n = 2) or the end of the luteal period (n = 2) of the following cycle. The mean interoestrous interval in the experimental group (123.3 +/- 23.1 day; n = 4) was significantly (p less than 0.001) shorter than the average of the mean values of the interoestrous interval (245.9 +/- 8.8 day; n = 36) of 10 control bitches. This shortening is mainly a consequence of a reduction to 35% of the anoestrous period of normally cyclic dogs. The luteal period of the first cycle was shortened to 78% compared with the luteal period of control dogs and this is also a contributing factor.