Effect of injection time of anti-PMSG antiserum on ovulation rate and quality of embryos in superovulated cows.

Eighteen cows were superovulated by injecting 3000 IU of PMSG during the luteal phase, followed 48h later with an injection of Estrumate. They were then placed in a control group or were given anti-PMSG antiserum at either 12h or 24h after the onset of oestrus. Sixteen of these animals were used for the same experiment five months later. The results were pooled because they were not significantly different between the two treatment periods. The timing of the injection of anti-PMSG antiserum, either 12h (11 cows) or 24h (12 cows) after the onset of oestrus, did not significantly affect the ovulation rate, the number of embryos collected or the number of good embryos. The antiserum significantly increased the number of good embryos but did not affect the ovulation rate or embryo recovery. It is concluded that even with a moderate dose of PMSG, the use of anti-PMSG at 12h or 24h after the beginning of oestrus improves the quality of embryos. The mean number of embryos to be transferred (5.5) is in the range of those obtained after the FSH treatments, but the procedure required only three injections compared with nine for the FSH treatment.