Resynchronization of ovulation and timed insemination in lactating dairy cows, II: assigning protocols according to stages of the estrous cycle, or presence of ovarian cysts or anestrus

Pregnancy rates were compared in lactating dairy cows ( n = 1083) assigned to protocols for resynchronization of ovulation based on stages of the estrous cycle, or presence of ovarian cysts or anestrus. Cows were detected not pregnant by ultrasonography 30 d after a previous AI (study day 0) and classified as diestrus, metestrus, proestrus, with ovarian cysts or anestrus. Cows in diestrus (January–May) were assigned to either Ovsynch (GnRH day 0, PGF 2α day 7, GnRH day 9, and timed-AI [TAI] 16 h later; n = 96), or Quicksynch (PGF 2α day 0, estradiol cypionate [ECP] day 1, AI at detected estrus [AIDE] on day 2, or TAI on day 3; n = 96). Cows in diestrus (June–December) were assigned to either Ovsynch ( n = 156) or Modified Quicksynch (PGF 2α day 0, ECP day 1, AIDE days 2 and 3, and to Ovsynch on day 4 if not detected in estrus; n = 142). Cows in metestrus were assigned either to Ovsynch ( n = 68), Heatsynch (GnRH day 0, PGF 2α day 7, ECP day 8, AIDE day 9, or TAI day 10; n = 62), or GnRH + Ovsynch (GnRH on day 0, followed by Ovsynch on day 8; n = 64). Cows in proestrus, with ovarian cysts, or anestrus were assigned to either Ovsynch (proestrus n = 89, ovarian cysts n = 97, anestrus n = 8) or GnRH + Ovsynch (proestrus n = 87, ovarian cysts n = 109, anestrus n = 9). Pregnancy rate was evaluated 30, 55 and 90 d after resynchronized AI. For cows in diestrus (January–May), pregnancy rates were higher for Ovsynch (35.9, 29.2 and 26.0%) than for Quicksynch (21.7, 16.7 and 15.6%). For cows in diestrus (June–December), pregnancy rates were similar for Ovsynch (34.4, 24.0 and 23.6%) and Modified Quicksynch (27.1, 26.2 and 21.6%). For cows in metestrus, pregnancy rates were higher for GnRH + Ovsynch (33.3, 24.5 and 20.3%) than for Heatsynch (20.3, 12.9 and 9.8%). For cows with ovarian cysts, pregnancy rates were higher for GnRH + Ovsynch (30.3, 26.6 and 22.9%) than for Ovsynch (20.2, 18.5 and 14.7%). Assignment to resynchronization protocols based on the stages of the estrous cycle, or presence of ovarian cysts improved pregnancy rates.