Development of Protocols to Synchronize Estrus in Beef Cattle

Development of protocols to manipulate the estrous cycle so all females are in estrus during a short, predefined period (synchronized estrus) while maintaining normal fertility has been a difficult goal to achieve; however, over the past two decades efficacious synchronization protocols have been created and are available to producers today. These protocols have been anticipated for a long time, but development of effective protocols depended on the creation and approval of products such as MGA, the CIDR, PGF2α, and GnRH as reviewed elsewhere. This manuscript was prepared to provide a review of estrus synchronization protocol development. Although Syncro-Mate B was one of the earlier products made available to beef producers it is no longer available in the U.S. today so I’ll only mention it briefly. Reviews are available if one is interested (Kesler and Favero, 1995, Kesler and Favero, 1996). Although unrelated to the loss of Syncro-Mate from the marketplace, an estrogen was included in the protocol. Estrogens have come under great scrutiny and availability of a protocol with an estrogen is unlikely today. Yet, a nearly identical product (Crestar) is available in some other countries (Nelis, 1995). Estrogen use will be discussed in more detail later in the manuscript.