Desempenho nutricional de bovinos em pastejo durante o período das águas com suplementação protéica ou protéico-energética

• Autor(a) principal: Costa, Viviane Aparecida Carli
• Data de Publicação: 2009
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/1729
• topic: Suplementação a pasto; Composto nitrogenados; Fontes de carboidratos; Pasture supplementation; Nitrogenous compounds; Sources of carbohydrates; CNPQ::CIENCIAS AGRARIAS::ZOOTECNIA::NUTRICAO E ALIMENTACAO ANIMAL

This thesis was prepared from two experiments with cattle grazing signal grass (Brachiaria decumbens Stapf.) pasture during the rainy season. The first experiment aimed to evaluate the effects of different chemical forms of nitrogenous compounds (protein and non-protein) and carbohydrates (starch and soluble fiber) on intake, digestibility, ruminal synthesis of microbial protein, nitrogenous compounds balance, and the transit and degradation dynamics of forage neutral detergent fiber (NDF). Five crossbred Holstein x Zebu steers, averaging 211±35 kg of body weight (BW) and fitted with rumen and abomasum canullae, were used. The treatments were: control (only pasture), and supplements based on corn plus soybean meal, corn plus urea, citrus pulp plus soybean meal, and citrus pulp plus urea. The supplements were balanced to present 30% of crude protein (CP), on dry matter (DM) basis, and provided at 3 g/kg BW. The experiment was carried out according to a 5 x 5 Latin square design, with five 15-day experimental periods. It was adopted a 2 x 2 + 1 factorial arrangement (two sources of nitrogenous compounds, two sources of carbohydrates and a control treatment). There was no interaction effect between sources of carbohydrates and nitrogenous compounds (P>0.10) for any variable. There were no effects of different sources of carbohydrates and nitrogen compounds on the estimates of diets components intake (P>0.10), except for indigestible NDF intake, which was lower (P<0.10) with supplementation with citrus pulp compared to corn (kg/d and g/kg BW) and lower (P<0.10) with supplementation with urea than soybean meal (g/kg BW). However, pasture intake decreased (P <0.10) with supplementation. The average substitutive coefficient was 2.11 g of DM of pasture/g of DM of supplement. Supplementation did not alter (P<0.10) the total and ruminal digestibility coefficients of DM, organic matter (OM) and NDF, and the dietary content of total digestible nutrients (TDN). However, the supplemented animals presented higher (P<0.10) ruminal and total digestibility coefficients of CP. The intestinal digestibility coefficients, rumen pH, rumen ammonia nitrogenous (RAN) concentration, and the nitrogenous compounds balance (NB) were not affected (P>0.10) by supplementation. The efficiency of microbial protein synthesis (EFIM) was not changed (P>0.10) by supplementation, averaging 123.1 g microbial CP/kg of TDN. However, supplementation based on corn caused higher EFIM (P<0.10) compared to citrus pulp (137.6 and 106.1 g microbial CP/kg of TDN, respectively). The degradation rate of forage NDF was decreased (P<0.10) by supplementation, but no significant differences were observed (P>0.10) among supplements. The average estimates of common rate of lag and degradation (&#955;) were 0.0486 and 0.0417 h-1 for not supplemented and supplemented animals, respectively. It was concluded that proteinenergy supplements for grazing cattle during rainy season do not improve nutritional performance, which reflects the high substitutive effect caused by supplements. The second experiment aimed to evaluate the effect of different true protein:non-protein nitrogen ration in supplements on intake, digestibility, ruminal synthesis of microbial protein, nitrogenous compounds balance, and the transit and degradation dynamics of NDF. Five crossbred Holstein x Zebu steers, averaging 335±35 kg of BW and fitted with rumen and abomasum canullae, were used. The treatments were: control (only pasture), and supplements based on urea (U), 2/3 of nitrogenous compounds from urea and 1/3 of nitrogenous compounds from albumin, 1/3 of nitrogenous compounds from urea and 2/3 of nitrogenous compounds from albumin, and albumin (A). It were supplied 200 g/d of CP from supplements. The experiment was carried out according to a 5 x 5 Latin square design, with five 15-day experimental periods. There were no effects of supplementation on voluntary intake (P>0.10), except on CP intake, which was increased by supplementation (P<0.10). The replacement of urea by albumin in the supplements caused linear and cubic effects (P<0.10) on the CP and digested NDF intakes, respectively. Other diet components intakes were not affected by the supplement composition (P>0.10). Supplementation did not affect (P>0.10) the total digestibility coefficients or the diet content of TDN. Supplementation increased (P<0.10) ruminal apparent digestibility coefficient of CP, which moved from negative (P <0.10) for the control treatment to positive, but not different from zero (P> 0.10), for treatments involving supplementation. The supplementation increased the rumen pH and RAN concentration (P<0.10). The NB was enhanced by supplementation (P<0.10). The replacement of urea by albumin caused a cubic effect on the BN (P<0.10), with the higher value obtained at 1/3 of supplemental CP as urea. The EFIM was not influenced (P>0.10) by supplementation or supplement composition. The supplementation increased the estimates of &#955; (P<0.10). The supplementation with ruminal degradable nitrogenous compounds for grazing cattle during rainy season increases the efficiency of use of pasture mainly by improve the body nitrogenous compounds retention.