Exigências de proteína e energia de bovinos nelore confinados

Abstract

An experiment was carried out with 30 non-castrated Nellore cattle with initial mean body weight of 380.2 ± 28.7 kg, to evaluate the prediction equations of the physical and chemical composition of the carcass and the empty body chemistry developed by Hankins and Howe (1946); Valadares Filho et al. (2006) and Marcondes et al. (2012) and to predict the energy and protein requirements for maintenance and gain of Nellore cattle not castrated. Five animals were slaughtered early in the experiment to getting body composition and initial body weight (EBW). The remaining cattle were randomly distributed in four treatments, in a completely randomized design: maintenance (diet containing 60% Tifton 85 hay and 40% concentrate, supplying 1.2% of body weight per day) and increasing levels of concentrate 17%, 34%, 51% and 68% available for consumption ad libitum (10% leftover from the offered). After 112 days of confinement the animals were slaughtered. The digestive tract was emptied and weighed along with the heart, lungs, liver, spleen, pancreas, shavings, reproductive tract, fat, kidneys, tail, head, leather, limbs, carcass and blood to obtain empty body weight. From the left half carcass, after weighing, the section was removed between the 9th and 11th ribs and weighed for further separation and weighing of the bone, muscle and adipose tissues of the left half carcase and the rib section and subsequent To obtain dry matter (DM), crude protein (CP), ethereal extract (EE) and water. In addition, the other non-carcass components were milled and sub-samples were taken for DM, CP, EE and water analysis. The requirements for uncastrated male Nelore cattle of net energy for gain are obtained by the equation: RE = 0.0430 * EQEBW0.75 * SWG1.3595. The need for liquid and metabolizable energy for maintenance is 78.99 and 116.13 kcal / kcal/EBW0.75 / day. The efficiencies of the use of metabolizable energy for maintenance and gain are 68.01% and 46.50%, respectively. The equation: PLg = 131.8 * GEBW + 22.78 * RE, predicts net daily protein requirements for weight gain of confined and uncastrated male Nellore cattle. The requirement for metabolizable protein for maintenance was 4.81 g / kg EBW0.75 /day. The efficiency of use of the metabolizable protein for weight gain was 51.5%. In non-castrated Nellore cattle, the equations of Hankins and Howe (1946) improve the physical and protein composition and ethereal extract in the carcass.The water in the carcass was better estimated by the model of Valadares Filho et al. (2006). The prediction of protein, ethereal extract and water in the empty body was better estimated by Valadares Filho et al. (2006). The equations proposed by Marcondes et al. (2012) were less adequate to estimate the chemical composition of the carcass and the empty body of the animals used. It is recommended the adjustment and validation of the prediction equations of the chemical composition of the carcass of Nellore cattle not castrated.