Progesterone administered after insemination did not affect the fertility of cattle following a controlled breeding program

Abstract

Oestrus and ovulation were induced in 112 suckled beef cows following intravaginal administration of progesterone (CIDR-B) and pregnant mare serum gonadotrophin (PMSG). Supplementary progesterone was provided during the induced luteal phase by re-treatment with CIDR-B from 6-21 or 10-21 days after initial insemination. A control group did not receive supplementary progesterone Supplementary progesterone did not affect the pregnancy rate to the initial insemination (59%). It did, however, tend to increase the proportion of non pregnant cows detected in oestrus 21-24 days after the initial insemination (17131 v. 3/14, P<0.05), but the fertility of treated and control cows inseminated at this second oestrus was not significantly different (30%).