Disponibilidade de energia líquida no leite e desempenho ponderal de bezerros Hereford e Aberdeen Angus do nascimento à desmama

Abstract

This research aimed at evaluating ponderal performance of the calves from birth to 189 days of age. Ninety-five calves were used (55 Aberdeen Angus and 40 Hereford), grazing natural pasture. Milk production of cows was estimated by the weight-suckled-weight method, and ponderal performance of the calves was evaluated in 21-day intervals from birth. Calving season was divided at time 1 (September) and time 2 (October). For analyses, it was included in the statistical model as fixed effects, breed of the cows, calf sex in the calving season, calving order and pregnancy. Data were submitted to statistical analyses, adopting 0.5 as critical levels of probability. Breed of the dams influenced calves weaning weight, average daily weight gain and cow efficiency, with 191.90 and 163.02 kg, 0.78 and 0.64 kg, and, 45.24 and 39.40%, for Aberdeen Angus and Hereford, respectively. Multiparous cows were superior to primiparous on weight of the calves on birth and on weaning on average daily weight gain. Calving season affected weights of the calves on birth and on weaning, average daily weight gain and total milk production with the following values for September and October: 31.15 and 37.19 kg; 183.63 and 171.29 kg; 0.76 and 0.67 kg; and, 1,605.04 and 1,378.78 kg, respectively. September was the best time for calf weight at weaning, average daily weight gain and total milk production, while October was better only for birth weight. Performance of calves is not influenced by their sex neither by pregnancy. © 2010 Sociedade Brasileira de Zootecnia.