OVARIAN RESPONSE OF DAIRY COWS TO PROGESTERONE COMBINED ON ESTRUS SYNCHRONIZATION USING GnRH-PGF2 alpha BASED PROTOCOL

The objective of this study was to evaluate the response of ovaries in estrus synchronization protocol using GnRH-PGF2 alpha based protocol combined progestin in a herd with tie-stall housing system. A total of 20 Holstein Friesian cows at different stages of estrus cycle in a dairy herd were enrolled in the present study. The cows were randomly allocated into two treatment groups; with and without CIDR (Controlled internal drug release) insertion. All cows received 100 mu g of GnRH I. M. at the beginning of the treatment (d 0) without regard to the stages of the estrus cycle followed by 25 mg PGF2 alpha IM 7days later. Cows in CIDR group were inserted CIDR into the vagina at the time of GnRH administration and were removed on the day of PGF2 alpha administration. estrus signs were checked twice daily starting on day-2 after initiation of the protocol, except cows in CIDR group the estrus signs were checked starting on day-8 of the protocol. The animals showing estrus signs were noted. Blood samples were collected from all animals on the days of GnRH and PGF2 alpha treatments and on day-10 after initiation of protocol for progesterone concentration. The results of this study showed that 30% animals in cows without CIDR insertion showed estrus signs prior to PGF2 alpha injection. Involving CIDR to synchronized estrus with GnRH-PGF2 alpha based protocol avoided the occurrence of premature estrus and maintained high progesterone concentration on the day of PGF2 alpha administration. It is concluded that ovarian response after involving CIDR in the protocol for estrus synchronization especially using combination of GnRH and PGF2 alpha were much effective to synchronize the initiation of estrus in dairy cows. Likewise, the use of progesterone avoided premature estrus.