Composição corporal e requisitos energéticos de bovinos de corte sob suplementação em pastejo

Abstract

The objective in this trial was to estimate the energy requirements of supplemented Zebu bulls grazing Brachiaria decumbens paddocks. Twenty eight intact males, seven months old and initial body weight 180 kg were used. Eight animals were slaughtered as reference, in different weight ranges. The net energy requirements for weight gain were obtained by regressing the log of the retained energy (RE) on the log of empty body weight (EBW). The net energy requirements for maintenance (NEm) were obtained from regression of the log of the heat production (HP) on the metabolizable energy intake (MEI). The efficiency of metabolizable energy use for maintenance (km) was calculated as the ratio of net energy requirements for maintenance to metabolizable energy for maintenance (MEm) and the slope of the linear regression of retained energy on metabolizable energy intake was considered as an estimate of the efficiency of using metabolizable energy for weight gain (kg). The net energy requirements for maintenance of Zebu bulls, under pasture, was 82.4 kcal/EBW0.75/day or 76.12 kcal/BW0.75/day. Thus, grazing Zebu bulls have about 5% greater net energy requirements for maintenance than feedlot Zebu bulls. The daily requirements of metabolizable energy was 149.76 kcal/EBW0.75, and the efficiency of metabolizable energy used for maintenance (km) of Zebu bulls under pasture was 55% and for gain (kg) 29%. © 2009 Sociedade Brasileira de Zootecnia.