Abstract
Numbers of estrus synchronization programmes are available in cattle based on the use of various hormones like progesterone, prostaglandin F2a and their various combinations with other hormones like estrogen and Gonadotrophin Releasing hormone (GnRH). Selection of appropriate estrus synchronization protocol should be made on the basis of management capabilities and expectations of the farmer. Synchronization of oestrus can be accomplished with the injection of prostaglandin F2a alone, but it needs proper detection of the ovarian status of the cows as prostaglandin F2a is active in only functional corpus luteum in between 8 to 17 days of estrous cycle. Progesterone may reduce fertility up to 14 percent, but short time progesterone exposure (less than 14 days) is beneficial. Addition of GnRH in the Progesterone or Prostaglandin based synchronization programme is helpful for more synchrony in estrus as GnRH may be helpful to synchronize the oestrous cycle in delayed pubertal heifers and post partum cows (Post partum anoestrum) and further a single, timed artificial insemination is possible with this method. New methods of synchronizing estrus in which the GnRH-PG protocol is preceded by progesterone treatment offer effective synchronization of estrus with high fertility.
Highlights
Synchronization of estrus implies the manipulation of the estrous cycle or induction of estrus to bring a large percentage of a group of females into estrus at a short, predetermined time (Odde, 1990)
Several authors described the experiments that have been conducted since the discovery of ovarian steroids and which have lead to the effective control of the length of the bovine estrous cycle and the timing of estrus and ovulation (Hansel and Schechter, 1972; Hansel and Beal 1979; Patterson et al, 1989; Odde, 1990; Larson and Ball, 1992)
Combination of (GnRH) with the Prostaglandin F2a (Prusley et al, 1994; Prusley et al, 1995 a, b) and Progesterone (Patterson et al, 1999) based synchronization programme has shown a new direction in the estrus synchronization of cattle with the manipulation of follicular development
Summary
Synchronization of estrus implies the manipulation of the estrous cycle or induction of estrus to bring a large percentage of a group of females into estrus at a short, predetermined time (Odde, 1990). Synchronization of estrus is one of the advanced managemental process through which the humane errors and managemental costs could be minimized It is beneficial in Sheep, where timely heat detection is difficult due to exhibitions of less external heat symptoms and in large cattle herd. Combination of (GnRH) with the Prostaglandin F2a (Prusley et al, 1994; Prusley et al, 1995 a, b) and Progesterone (Patterson et al, 1999) based synchronization programme has shown a new direction in the estrus synchronization of cattle with the manipulation of follicular development. A newer way of creating estrous synchrony is by using gonadotropin-releasing hormone (GnRH) or an analogue, which causes ovulation of a large follicle. This help in synchronizing estrous cycle in anoestrous female
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