Fertility of ewes treated with prostaglandin F2α and artificially inseminated at predetermined intervals thereafter

Abstract

An experiment was conducted to investigate the fertility rate in ewes inseminated with either fresh undiluted or frozen-thawed ram semen, without the use of vasectomized rams, at the first synchronized oestrus after a single intramuscular injection of 16 mg prostaglandin F2α (PGF2α). It was also investigated whether two injections of PGF2α at an interval of 12 days would improve the degree of synchronization of oestrus and the subsequent fertility. The degree of synchronized oestrus with two injections was similar to that with a single injection (72%v. 74% respectively). Inseminations at 46 and 54 hr or at 70 and 78 hr after treatment showed fertility comparable with that from those inseminations at oestrus detected by vasectomized rams (50% v. 45% for fresh undiluted semen and 22% v. 25% for frozen-thawed semen respectively). Inseminations at 70 and 78 hr after treatment showed a much higher fertility rate for both fresh undiluted (62% v. 39% respectively) and frozen-thawed semen (39% v. 9% respectively) than inseminations at 46 and 54 hr. Two injections of PGF2α resulted in similar fertility rates in control ewes following insemination with either fresh undiluted semen (50%) or frozen-thawed semen (22%).