Desempenho produtivo e exigências nutricionais de bovinos de corte em pastagens de Brachiaria decumbens, com suplementação protéica

• Autor(a) principal: Paixão, Mônica Lopes
• Data de Publicação: 2008
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/1703
• topic: Bovino de corte; Exigência; Proteína; Beef cattle; Requeriments; Protein; CNPQ::CIENCIAS AGRARIAS::ZOOTECNIA::NUTRICAO E ALIMENTACAO ANIMAL

This thesis was elaborated from six experiments that aimed to evaluate the effects of different protein sources on performance and nutritional parameters of beef cattle supplements during of the dry, dry-rainy and rainy seasons, in Brachiaria decumbens pasture, as well as to estimate the body composition and the energy, protein, and macrominerals requirements of grazing beef cattle during the rainy season. In Experiment 1 (Dry Season), 20 castrated steers with average initials age of 10 months and weight of 254,70 ± 24,09 kg were used. The protein sources evaluated were corn gluten meal 21% CP + wheat middlings + urea (FGM); cracked bean (FEIT); whole bean (FEII); wheat middlings + urea (FTR) and rice bran + urea (FAR). There was difference for average daily gain (P<0,10), and the values, in kg per day, were 0,571; 0,432; 0,506; 0,676 and 0,614, respectively. In Experiment 2 (Dry-rainy and rainy seasons), 16 castrated steers with average age and weights of 15 months and 339,75 ± 42,35 kg were used. It were evaluated a mineral mixture (MM) and different protein sources: whole bean + wheat middlings + urea (FEI); wheat middlings + urea (FTR) and rice bran + urea (FAR). There was no difference for average daily gain, and the values, in kg per day, were 0,433; 0,588; 0,514 and 0,416, respectively. In Experiment 3 (Dry Season), 20 castrated calves with average initials ages and weights of 10 months and 185,90 ± 21,47 kg were used. The protein sources evaluated were soybean meal (FSO); cottonseed meal (FAL); corn gluten 60% CP (GLM); peanut meal (FAM) and self-feed supplement (AC). There was no difference for average daily gain, and the values, in kg per day, were 0.524; 0.486; 0.470; 0.518 and 0.505, respectively. In Experiment 4 (Dry-rainy and rainy seasons), 20 intact calves with average initials age and weights of 10 months and 258,10± 29,52 kg were used. It were evaluated a mineral mixture (MM) and different protein sources: soybean meal (FSO); corn gluten 60% CP (GLM); peanut meal (FAM) and self-feed supplement (AC). There was difference (P < 0.10) for average daily gain between protein supplemented and non-supplemented animals, and the values, in kg per day were 0,351; 0,529; 0,688; 0,519 and 0,574 respectively. In Experiment 5 (Rainy season), five Holstein-Zebu steers, fistulated in rumen, abomasum and esophagus, with average initial weight of 196 kg, were used to evaluate the apparent digestibility and ruminal digestibility, as well as for sampling the pasture through esophageal collection. The protein sources evaluated were corn gluten 21% CP + wheat middlings + urea (FGM), whole bean + wheat middlings + urea (FEI), wheat middlings + urea (FTR), and rice bran + urea (FAR). There was difference (P <0,05) only for intake of ether extract. In Experiment 6, the nutrient intake, the energy concentration of diets, the body composition, as the requirements of energy, protein and macrominerais, of grazing bulls were evaluated. There was used 24 intact bulls with initial live weight (LW) of 339 kg and average age of 15 months. Four bulls were slaughtered at the beginning of the trial, after the adaptation period, to be used as reference to estimate the initial empty body weight (PCVZ) and body composition of the others bulls. The 20 remaining animals, were allocated in a complete randomized design, in five treatments: restricted grazing time to limit energy intake to a level close to the maintenance level, or fed the following supplements: mineral mixture (MM), whole bean + wheat middlings + urea (FEI); wheat middlings + urea (FTR) and rice bran + urea (FAR). The fat, protein, energy and macrominerais (Ca, P, Na, K and Mg) contents were obtained as a function of the logarithm of PCVZ. The net energy requirement for maintenance was estimated as the anti-log of the intercept of the linear regression of the logarithm of the heat production (PC) on the metabolizable energy intake. The intake of crude protein, non-fibrous carbohydrate and ether extract were different (P <0,05), in which the protein supplemented animals had higher intakes than non- supplemented animals. The retained energy and the daily weight gain were lower for animals of the maintenance treatment. The efficiencies of utilization of metabolizable energy (MEEU) for maintenance (km) and gain (kg) were estimated from the relationship between the net energy concentration, for maintenance or gain, respectively, and the metabolizable energy (ME) content of the diet. The amount of energy and fat in the gain increased as the body weight of the animals increased. The net energy requirements for gain (NEg) of zebu steers can be obtained by the equation: NEg = 0,0397*BW0,75*EBG1,1982. The daily net energy requirement for maintenance was 74,01 kcal/BW0,75. The estimated value for km was 0.53 and for kg was 0.32. The protein requirements for gain decreased as the BW increased. The protein requirement found for an animal with 250 kg, was of 193 g/kg EBG while for an animal of 400 kg was 187 g/kg EBG. An equation was obtained to estimate the retained protein (RP) as a function of the weight gain (ADG) and the retained energy (RE): RP = 16,2036 + 234,3105*ADG - 31,4027*RE. The requirements of metabolizable protein for maintenance and for weight gain were of 358and 380 g/kg BW, respectively, for a 400 kg bull under grazing. The net requirements for gain of calcium, phosphorus and magnesium decreased with the increase of the weight of the animals. The relationships of retained Ca and P with the retained protein were 7.56 g Ca/100 g retained CP and 4,94 g P/100 g retained CP.