Synchronization of ovulation in yaks (Poephagus grunniens L.) using PGF2α and GnRH

The objective of this study was to test the efficacy of estrus synchronization in yaks using the Ovsynch protocol. To eight non-lactating cycling yaks were administered GnRH analogue followed by PGF2α analogue treatment 7 days later and further injected with a second injection of same GnRH analogue 2 days after the PGF2α analogue administration. Ovulation was detected by rectal palpation at 2 h intervals from the initial signs of estrus till ovulation. For LH and progesterone the blood samples were collected at 15 min intervals starting from 1 h prior to the second injection of GnRH analogue until 6 h later and further at 2 h intervals till 2 h after the ovulation. Ovulation was detected in seven out of eight yaks after Ovsynch treatment. The mean time interval from the second GnRH injection to ovulation was 24.8 ± 1.95 h with a range of 20–34 h and the mean interval from the LH peak and ovulation was 19.96 ± 1.91 h with a range of 14–29 h. The high degree of ovulation synchronization could be attributed to the highly synchronized LH peaks in the treated animals. It was concluded that this estrus synchronization protocol could be applied for fixed time AI in yak.