Reproductive parameters in Holstein dairy cows treated with three resynchronization methods

Abstract

The objective of the present study was to determine the reproductive parameters in Holstein cows treated by different hormonal protocols during insemination and postpartum periods. The 114 dairy cows (multiparous) with BCS between 2.75 and 3 were divided into 3 groups in a completely randomized design. 38 cows were treated by Heatsynch method + eCG (M 1), 38 cows received Ovsynch + CIDR (M 2) and 38 cows were subjected to the Heatsynch method (M 3). Blood samples were taken to determine progesterone plasma contents in 14, 21 and 24 days after first insemination. Results showed that treatment with M 2 protocol significantly decreased days to first service and conception rate in the cows (P < 0.05). First service conception rate in cows treated with M 1 protocol was higher (P < 0.05) compared to M 2 and M3 protocol. Pregnancy rate in M 1 was significantly higher than that of the other groups (P ≤ 0.05). This difference could be due to equine chorionic gonadotrophin (eCG) which could have an effective function on ovulation, fertilization and embryo's vitality. Plasma progesterone levels of pregnant cows were higher than that of nonpregnants cows regardless the type of resynchronization protocols (P≤0.05). However, activation of ovaries, reinitiate estrous cycle and accordance between estrous and ovulation were increased when dairy cows subjected to the Heatsynch + eCG method (M 1). Thus, M 2 protocol is recommended for primiparous but not for multiparous cows, and T 3 protocol is not recommended for synchronization.