Consumo, digestibilidade e dinâmicas de trânsito e degradação da fibra em detergente neutro em bovinos alimentados com forragem tropical de baixa qualidade e compostos nitrogenados

• Autor(a) principal: Lazzarini, Isis
• Data de Publicação: 2007
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/5842
• topic: Bovino de corte; Suplementação; Repleção ruminal; Degradação; Beef cattle; Supplementation; Rumen fill; Degradation; CNPQ::CIENCIAS AGRARIAS::ZOOTECNIA::NUTRICAO E ALIMENTACAO ANIMAL

The objective of this work was to evaluate the effects of supplementation with nitrogenous compounds on intake, digestibility, and transit and degradation dynamics of neutral detergent fiber in cattle fed low-quality tropical forage. Five crossbred heifers, with average live weight of 209 kg and fitted with ruminal cannulae, were used. The animals were fed ad libitum with signal grass (Brachiaria decumbens Stapf.) hay, which had crude protein (CP) content of 5.08% of dry matter (DM). The five treatments were defined according to the increasing level of CP in the diet (0, 3, 5, 7, and 9 percentile points above the CP level of the roughage). The supplement was a mixture of urea, ammonium sulfate, and albumin (4.5:0.5:1.0, respectively). The experiment was carried out according to a 5 x 5 Latin square design, with five experimental periods. The average CP levels in the diets were: 5.28, 8.08, 9.82, 11.87, and 13.63% in DM basis. The intakes of DM, OM, NDF, and NDFom(n) showed a quadratic response according to CP levels in the diet (P<0.10), with maximum responses on 10.83%, 10.78%, 10.43%, and 10.37% of CP, respectively. The digestibility coefficients of OM and NDF showed a linear-response-plateau (LRP) according to CP levels (P<0.10), with plateau beginning (maximum response) on 7.93% and 7.55% of CP, respectively. The average daily concentration of rumen ammonia nitrogen (RAN) was positively related with CP levels (P<0.10). The RAN estimate associated with the maximum DM intake was 15.33 mg/dL. It was observed that intestinal flow of microbial nitrogenous compounds and nitrogen intake become equivalent each other on 7.13% of CP. There was no relationship between CP levels and efficiency of microbial synthesis (P>0.10). The potentially degradable fraction of NDF was linearly increased (P<0.10) according to CP levels in diet until 8.62% CP. From this point, there was stabilization of estimates (47.92% of NDF). On the other hand, the degradation rate of potentially degradable NDF showed a quadratic response (P<0.10) to CP levels, with maximal response on 13.39% of CP. The rumen rate of passage of fibrous particles, the mean retention time in the rumen, and the rumen fill effect of undegradable NDF showed a LRP (P<0.10) according to CP levels in the diet, with plateau beginning on 7.59, 7.68, and 8.00% of CP, respectively.