Ninety-four percent of cows responded to the initial synchronization with estrous behavior and normal concentrations
of progesterone in plasma. This is a greater percentage than in previous studies when beef and
dairy cows and heifers (Britt et al., 1978; Nkuuhe and Manns, 1985) were synchronized with 2 PGF2α treatments
11 to 12 d apart. All cows had normal estrous cycles at the beginning of this study, which probably increased the response rate to the initial synchronization. In addition, a greater number of estrous events were probably detected because cows were monitored continuously with HeatWatch.