Effects of liveweight gain during pregnancy of 15‐month‐old Angus heifers on dystocia and birth weight, body dimensions, estimated milk intake and weaning weight of the calves

摘要

Abstract First‐calving, 2‐year‐old heifers are particularly susceptible to dystocia caused by foeto‐maternal disproportion. Forty‐four 15‐month‐old Angus heifers were allocated to either a moderate (583 ± 73 g/day) or low (193 ± 71 g/day) liveweight gain treatment for the first trimester (93 days) of pregnancy. Both groups were of similar liveweight at parturition. Birth weight of the calves and incidence of dystocia were not significantly different between treatment groups at 33.0 ± 0.7 kg, compared with 33.8 ± 0.6 kg and 12% compared with 22% for the moderate and low groups, respectively. Body dimensions, liveweight from birth to 205 days of age and estimated milk intake of the calves were generally not affected by treatment. Assisted calves had greater estimated milk intake than unassisted calves at 37 days of age (5.9 ±1.0 versus 4.1 ± 0.6 kg/day; P < 0.05). Liveweight gain in early pregnancy did not affect birth weight of calves or the incidence of dystocia in 2‐year‐old heifers.