Effects of temperament and acclimation to handling on reproductive performance of Bos taurus beef females

摘要

Two experiments evaluated the effects of temperament and acclimation to handling on reproductive performance of Bos taurus beef females. In Exp. 1, 433 multiparous, lactating Angus × Hereford cows were sampled for blood and evaluated for temperament before the breeding season. Cow temperament was assessed by chute score and exit velocity. Chute score was assessed on a 5-point scale according to behavioral responses during chute restraining. Exit score was calculated by dividing exit velocity into quintiles and assigning cows with a score from 1 to 5 (1 = slowest, 5 = fastest cows). Temperament score was calculated by averaging chute and exit scores. Cows were classi? ed for temperament type according to temperament score (≤ 3 = adequate, > 3 = aggressive). Plasma cortisol concentrations were greater (P < 0.01) in cows with aggressive vs. adequate temperament. Cows with aggressive temperament had reduced (P ≤ 0.05) pregnancy and calving rate and tended to have reduced (P = 0.09) weaning rate compared with cows with adequate temperament. Hence, kilogram of calf born per cow was reduced (P = 0.05) and kilogram of calf weaned per cow tended to be reduced (P = 0.08) in aggressive cows. In Exp. 2, 88 Angus × Hereford heifers (initial age = 206 ± 2 d) were weighed (d 0 and 10) and evaluated for temperament score (d 10). On d 11, heifers were ranked by these variables and assigned to receive or not (control) an acclimation treatment. Acclimated heifers were processed through a handling facility 3 times weekly for 4 wk (d 11 to 39; Mondays, Wednesdays, and Fridays), whereas control heifers remained undisturbed on pasture. Heifer puberty status, evaluated via plasma progesterone concentrations, was assessed on d 0 and 10, d 40 and 50, 70 and 80, 100 and 110, 130 and 140, 160 and 170, and 190 and 200. Blood samples collected on d 10 and 40 were also analyzed for plasma concentrations of cortisol and haptoglobin. Temperament score was assessed again on d 40 and d 200. Acclimated heifers had reduced (P = 0.01) concentrations of cortisol and haptoglobin on d 40 and reduced (P = 0.02) exit velocity on d 200 compared with control heifers. Puberty was hastened in acclimated heifers compared with control (P = 0.01). Results from this study indicate that B. taurus beef cows with aggressive temperament have impaired reproductive performance compared with cohorts with adequate temperament, whereas acclimation to human handling after weaning hastens reproductive development of replacement heifers.