The P4 injection dosage of 50 and 100 mg could induce new follicular wave efficiently, and there was no significant difference on estrus synchronization and superovulatory results between the BI and PRD groups (P > 0.05).

• 外源注射50和100mgP4都能够成功地诱导新的卵泡波的发生；同期发情效果和超排效果没有显著差异(P>0.；05)。