Effect of duration of PMSG treatment on induction of oestrus, pregnancy rates and the complications of hyper-oestrogenism in dogs.

In anoestrous bitches, the use of 5 or 10 days of daily PMSG treatments (20 i.u./kg/day) before a single injection of hCG (500 i.u./dog) did not affect the timing of induced pro-oestrus (4-6 days) but did result in a greater incidence of conception (3 of 6 vs 6 of 17), a high rate of successful pregnancy (50% vs 0%), lower preovulatory oestrogen concentrations, and reduced incidence of complications due to hyper-oestrogenism such as thrombocytopenia (0% vs 29%). These results suggest an advantage of 5 over 10 days of priming with PMSG, at the doses used before hCG injection, for induction of fertile oestrus in bitches.