Composição corporal e exigências nutricionais de bovinos Nelore castrados em pastejo / Body composition and nutritional requirements of Nellore steers under grazing

AUTOR(ES)
DATA DE PUBLICAÇÃO

2008

RESUMO

The present work was done aiming to determine the body composition and energy, protein, calcium (Ca), phosphorus (P), magnesium (Mg), potassium (K) and sodium (Na) requirements. Twenty four Nellore steers averaging 371 14 kg of initial body weight and 26 months of age were used. Four calves were slaughtered at the beginning of the experiment (reference group), serving as a reference in subsequent studies. The remaining 20 animals were weighed and distributed in four treatments: mineral mixture, 0.3, 0.6 and 0.9% of body weight of supplementation. The experimental area was composed of eight paddocks, composed of Brachiaria brizantha cultivate Marandu. After the slaughter, all animal body parts were weighted and sampled. The samples were taken for determination of the oven dry, pre-degreased with ether, grinded and total nitrogen, ethereal extract and macrominerals concentrations were determined. The protein, fat, energy and macrominerals contents retained in the body were estimated by regression equations of the logarithm of protein, fat, energy or macrominerals body content, in function of the logarithm of empty body weight (EBW). The net protein, energy and macrominerals requirements, for gains of 1 kg EBW, were determined by means of the equation Y = b. 10a. Xb-1, being a and b the intercept and the regression coefficient of the prediction equations of the nutrients contents in the body, respectively. The net energy requirement for weight gain of zebu bulls can be obtained by the equation: NEg = 0.05764 x EBW0.75 x gain of EBW0.8328. The following equation was obtained to estimate the retained protein (RP), as a function of EBW gain and retained energy (RE): RP = PR = 28.9199 + 85.7301 gain of EBW + 8.0669 RE. The net protein requirement of Nellore decreased with the increase of the LW, being 174.62 and 163.10 g/kg of EBW gain for animals of 300 and 450 kg of LW, respectively. There was a decrease in the empty body and in the gain of empty body concentrations of the five macrominerals studied, with the increase of the live weight. The relationships g Ca/100g of retained protein and g P/100g of retained protein were 8.68 and 5.47, respectively. Total Dietary requirements of calcium e phosphorus were higher than recommended by the NRC (2000).

ASSUNTO(S)

energia proteína nelore protein requirements energy exigências nelore nutricao e alimentacao animal

ACESSO AO ARTIGO

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