Exigências nutricionais e componentes não carcaça de bovinos mestiços leiteiros

Abstract

The objective of this work was to evaluate the effect of the feed restriction and four concentrate level on the internal organs, viscera, gastrintestinal fill, and internal fat weight ofBulls dairy crossbred. We also evaluated too, the utilisation of the equations of the Hankins and Howe (1946), Valadares Filho et al. (2006) and Marcondes et al. (2012) for estimate of the chemical composition of the carcass and empty body, and energy and protein requirements these animals. We used thirty animals with an average weight of 339.1 kg. Five were slaughtered of the beginning of the trial, compounding the reference group, and the remaining after 112 days. The remaining were allotted to a completely randomized design with five treatments: 0; 17; 34; 51, and 68% of the dry mater in concentrate. The animals of the treatment with 0% of concentrate were submitted the feed restriction during the whole experimental period. Chemical composition was obtained of the right carcass half, and through samples between the 9th and 11th ribs (section HH) of the left carcass half. For prediction of the requirements was utilized the chemical composition of the right carcass half. The effect of the feed restriction was evaluated through of the average test. Regression equations were fitted to determine the effect of dietary concentrate inclusion on the variables. The equations that regard the composition chemical of the carcass and empty body were compared by mean square error of prediction and its components, concordance correlation coefficient (CCC) and distribution of the prediction errors. Requirements of metabolizable and net energy for maintenance were estimated by the regression among the heat production and the metabolizable energy intake (MEI). Use efficiency of metabolizable energy for gain was obtained by regression coefficient of the equation of the retained energy in function of MEI. Net energy requirement for gain (NEg) was estimated by equation of retained energy (RE) as a function of metabolic empty body weight (EBW0.75) and empty body weight gain (EBWg). Requirement of net protein for gain (NPg) was estimated by equation of the protein retained (PR) in function of the EBWg and RE. The use efficiency of metabolizable protein for gain was obtained by equation linear regression among the PR and the metabolizable protein intake (MPI). The ratio between the intercept of the regression of the MPI in function of the daily EBWg, by the average the of.EBW-0.75.day-1 EBW0.75 of the animals slaughtered at the end of the experiment, we obtained the requirement of the metabolizable protein for maintenance (MPm). The feed restriction caused smaller organ weights linked to energy metabolism, without influence on the heart and lungs. Viscera, gastrintestinal fill and internal fat are more influenced by the organs that increase the concentrate diet. In the bulls dairy crossbred confined, the equations of the Hankins & Howe (1946) estimated best the protein and water in the empty body, the models of the Valadares Filho et al. (2006) are most effective for prediction of the water in carcass and ether extract in the carcass and empty body, and the protein in the carcass these two models; while the equations proposed by Marcondes et al. (2012) were not effective to estimate the composition chemical of the carcass and empty body. For bulls dairy crossbred confined, the NEg is obtained by equation: NEg= 0.0448* EBW0.75* EBWg1.0996, the requirement of the metabolizable energy for maintenance is 138 kcal.EBW-0.75.day-1, the efficiency of metabolizable energy for maintenance and weight gain are 62.67% e 31,67%, respectively; the NPg is obtained by equation: NPg=242.34* EBWg – 23.09*RE; the efficiency of metabolizable protein for gain is 25.8%; the MPm is 2.96 g.EBW-0.75.day-1.