[Estrus induction in bitches by the administration of PMSG and HCG]

Oestrus was induced in 14 anoestrous beagle bitches by intramuscular injection of PMSG in a dose of 20 I.U./kg once daily on five consecutive days, followed by an additional single i.m. injection of 500 I.U. of hCG on the fifth day. The day on which the first injection was given was counted as Day 1 of the experiment. Between the fourth and sixth day, the bitches began to attract the attention of male dogs and between Days 9 and 15 all bitches came in heat. Matings occurred on two to ten occasions, and six of the bitches conceived. The maximum concentrations of oestradiol in the plasma were in most cases reached on Days 10 or 12 and ranged from 42 to 195 pg/ml. In all cases progesterone concentrations rose sharply between Days 10 and 20. The incretion phase of the corpora lutea was noticeably brief in the non-gravid bitches; in five of these eight bitches, anoestrous values below 2 ng/ml were already obtained before the 65th day of the experiment. These results indicate that the administration of PMSG on five consecutive days supplemented by a final single injection of hCG stimulates the ovaries adequately to afford good prospects of conception. The concentrations of ovarian hormones are discussed.