The incidence of elevated progestrone at the time of insemination in Suffolk ewes bred in August

The development of laparoscopic intrauterine insemination for sheep has been essential for the implementation of national Sire Reference Schemes in the UK (McKelvey and Simm, 1995). Whilst conception rate to artificial insemination (AI) has averaged 60-70% in most participating flocks, a number of flocks have experienced a proportion of their ewes returning to anoestrus following AI. This phenomenon restricts the implementation of sire reference schemes and it has been proposed that die causal factor could be the presence of a persistent corpus luteum at the time of insemination.