Inducing ovulation with the GnRH analogue dephereline in a five-day progesterone-based fixed-time AI protocol improves embryo survival in anestrous dairy cows

Abstract

This study compares the fertility effects of inducing ovulation using the GnRH analogue dephereline versus natural GnRH at the end of a 5-day progesterone(P4)-based protocol for fixed-time artificial insemination (FTAI) in heat-stressed and non-heat stressed anestrous lactating dairy cows. Cows were given GnRH (GnRH group, n = 676) or dephereline (DEPH group, n = 655) and inseminated 12 hours later. Based on odds ratios, pregnancy loss was 3.6 times more likely in cows carrying twins (P < 0.0001) and 0.4 times less likely in DEPH treated cows (P = 0.0005). No significant effects of treatment on the pregnancy rate were identified by binary logistic regression and the variables examined did not influence the twin pregnancy rate. In conclusion, compared to treatment with GnRH, dephereline given at the end of a 5-day P4-based protocol for FTAI reduced the risk of pregnancy loss regardless of the presence or absence of heat stress.