Effect of oestrous expression prior to timed artificial insemination with sexed semen on pregnancy rate in dairy cows

The objectives of the study were to determine (1) oestrous expression rate and (2) the effect of oestrous expression prior to progesterone‐based Ovsynch protocol on pregnancy rate in Holstein cows. All cows (n = 917) were subjected to 7‐day progesterone‐based Ovsynch protocol. In this protocol, cows that expressed oestrus before (HEAT1) the scheduled second GnRH were inseminated 20 h later after the onset of oestrus without GnRH administration. Cows that expressed oestrus after the second GnRH administration (HEAT2) or did not express oestrus (NOHEAT) received fixed‐timed AI. Oestrous expression was determined by using activity‐rumination monitoring system and all cows were inseminated with sexed semen. Oestrous expression rate prior to FTAI was 40.5% and the majority (p