Effects of presynchronization during the preservice period on subsequent ovarian activity in lactating dairy cows

Among the strategies aimed at overcoming difficulties in estrus detection in dairy herds, presynchronization with two PGF2α treatments 14 days apart before a timed AI protocol has been related to a significant increase in pregnancy rates. The aim of the present study was to evaluate the effects of presynchronization during the preservice period on subsequent ovarian activity in clinically normal lactating dairy cows. A second objective was to evaluate the incidence of reproductive disorders on Day 50 postpartum. Depending on the chronological order of parturition, cows were alternately assigned to a control (n = 102) or treatment (n = 101) group. Animals in the treatment group were administered two cloprostenol treatments 14 days apart, beginning on Day 22 postpartum. The reproductive tract of each animal was examined ultrasonographically on Days 43 and 50 postpartum to monitor ovarian structures and uterine contents. Blood samples were collected on Day 50 for progesterone determination. Cows were inspected for signs of estrus between Days 50 and 71 postpartum and were then inseminated. Follicular persistence rates were similar in the presynchronized (14.9%) and control (13.7%) groups. Cows in the presynchronized group showed a lower metritis-pyometra rate (0% < 3.9%; P = 0.045); a lower ovarian cyst rate (3% < 10.8%; P = 0.03); a higher luteal activity rate (progesterone concentrations ≥ 1 ng/ml) on Day 50 postpartum (76.2% > 52.9%; P = 0.0005); a higher estrus detection rate (73.3% > 47.1%; P < 0.0001); a higher ovulation rate (72% > 44%; P < 0.0001) and a higher pregnancy rate (29.7% > 15.7%; P = 0.02) than controls. Our results indicate that presynchronization during the preservice period reduces the incidence of ovarian cysts and metritis-pyometra determined on Day 50, and improves ovarian activity from Days 50 to 71 postpartum along with pregnancy rates in clinically normal lactating dairy cows. © 2003 Elsevier Science Inc. All rights reserved.