Validação das Equações Desenvolvidas por Hankins e Howe para Predição da Composição da Carcaça de Zebuínos e Desenvolvimento de Equações para Estimativa da Composição Corporal1

The equations developed by Hankins and Howe were validated in order to predict the physical and chemical carcass composition and equations were developed aiming to estimate the body composition of zebu cattle from the 9-10-11(th) rib cut composition. Nineteen Zebu steers, with 270 kg of initial live weight (LW) and 2 years old were used. Four were slaughtered in the beginning of the trial, performing the reference group, three were fed to the maintenance level and the remaining were uniformly allotted into three treatments, with different levels of concentrate in the diets (5, 35, 65%, in the total dry matter basis). Brachiaria brizantha and Cynodon spp haylage were used as the roughage source of the diets. The diets were isonitrogenous and the animals were fed ad libitum. The animals of the reference group and those of the treatments with 5, 35 and 65% of concentrate were fed for a period of, respectively, 84, 109, 104 and 102 days, after which the animals were slaughtered, with average body weight of 340.25; 360.55 e 374.50 kg, respectively. After slaughter, the right side of all carcasses were totally dissected. The same was done to the 9-10-11(th) rib cut, obtained from the left sides of carcasses. The physical composition of the carcasses were well predicted by the 9-10-11(th) rib cut, which chemical composition predicted satisfactorily the contents of protein, water and minerals of the zebu cattle carcasses. The content of fat of the carcasses was overestimated in 7.8%. A regression equation was developed to estimate the percentage of ether extract (EE) of the carcasses, in function of this component in the 9-10-11(th) rib cut: % EE carcass = 1.0709 + 0,7854 * % EE 9-10-11(th) rib cut, r(2) = 0.97. The empty body chemical composition can be predicted from the chemical composition of the 9-10-11(th) rib cut, however, more data should be gathered in order to develop equations that would be applicable in a wide range of situations, producing reliable estimates.