Abstract
Various programs have been used to synchronize ovulation of a fertile oocyte, accompanied by fixed-time artificial insemination (FTAI). These programs involve a series of hormonal treatments to achieve four physiologic outcomes: 1) synchronize an ovarian follicular wave; 2) optimize conditions for ovulatory follicle development; 3) synchronize corpus luteum (CL) regression; and 4) synchronize ovulation. This manuscript summarizes studies conducted in Brazil with lactating dairy cows that aimed to increase pregnancy rates to E2/P4-based programs.
Highlights
Recent reviews have considered the history, physiological basis, and practical use of FTAI for reproductive management of dairy cattle (Baruselli et al, 2012; Binelli et al, 2014; Wiltbank and Pursley, 2014)
This review will examine some specific published research manuscripts that were done with ample statistical power (>200 cows/treatment) and, in our opinion, have been critical for the development of the programs that are in current use for FTAI in dairy cattle in Brazil
Increasing the length of the protocol for FTAI increased the percentage of cows detected in estrus and reduced pregnancy losses
Summary
Recent reviews have considered the history, physiological basis, and practical use of FTAI for reproductive management of dairy cattle (Baruselli et al, 2012; Binelli et al, 2014; Wiltbank and Pursley, 2014). An experiment (Vasconcelos et al, 2011b) was done to compare effects of two protocols for synchronization of ovulation (GnRH- vs E2-based protocols) on P4 concentrations and fertility in lactating dairy cows subjected to either FTAI or fixed-time embryo transfer (FTET).
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