Effects of induced parturition and early obstetrical assistance in beef cattle.

Pregnant crossbred beef females (33 second-calf cows and 73 primiparous heifers) bred to a single Hereford sire were assigned to a 2(3) factorial study involving age of dam, natural (NP) or induced (IP) parturition and late emergency (LA) or forced early (EA) obstetrical assistance. Parturition was induced with 10 mg flumethazone given i.m. between 1400 and 1600 on d 272 of gestation; EA was given when the cervix and birth canal were fully dilated. Average IP occurred 39.6 h postinjection, and 95.3% of the treated dams responded within 60 h postinjection; gestation was shortened 2.9 d (P approximately equal to .07). Dystocia score (from 1 = no assist to 4 = major traction required and 5 = abnormal presentation) was 1.12 vs 2.40 for LA and EA, respectively (P less than .01), and 11% of LA vs 84% of EA were assisted. Calf vigor score (1 = normal to 3 = severely depressed or dying) at birth was 1.3 for NP and 1.1 for IP (P approximately equal to .06) and 1.3 for EA and 1.1 for LA (P less than .05). This effect of EA was due to reduced vigor of calves experiencing abnormal presentation. Birth weights (BW) and weaning weights (WW) of calves from cows exceeded those from heifers (32.6 vs 30.8 kg, P less than .05; 210.9 vs 156.3 kg, P less than .01, respectively). Differences due to IP and EA in BW, WW, postpartum interval and conception rate were not significant, but weight gain of calves from EA dams tended (P approximately equal to .09) to be greater than weight gain of calves from LA dams.(ABSTRACT TRUNCATED AT 250 WORDS)