Intake, digestibility, and rumen dynamics in cattle fed low- quality tropical forage and supplemented with nitrogenous compounds and (or) carbohydrates / Consumo, digestibilidade e dinâmica ruminal em bovinos alimentados com forragem tropical de baixa qualidade e suplementados com compostos nitrogenados e/ou carboidratos

AUTOR(ES)

Marjorrie Augusto de Souza

DATA DE PUBLICAÇÃO

2007

RESUMO

The objective in this work was to evaluate the effects of supplementation with nitrogenous compounds and (or) carbohydrates on intake, digestibility, microbial protein synthesis and neutral detergent fiber (NDF) dynamics in rumen, in cattle fed low-quality tropical forage. Four Holstein x Zebu heifers, with average live weight of 231.9 kg and fitted with ruminal canullae, were used. The animals were fed ad libitum with signal grass (Brachiaria decumbens Stapf.) hay (5.16% of CP as DM basis). The treatments were: control (only hay); hay with nitrogenous compounds for elevating the CP of the forage at 10%; hay with carbohydrates at the level of 20% of forage intake; and hay with nitrogenous compounds and carbohydrates, as described above. The protein supplement was a mixture of urea, ammonium sulfate, and albumin (4.5:0.5:1.0, respectively). The corn starch was used as carbohydrate supplement. The experiment was carried out according to a 4 x 4 Latin square desing in a 2 x 2 factorial arrangement. There was positive effect (P<0.10) of nitrogenous compounds supplementation on DM, OM, and NDFom(n) intakes. On the other hand, the carbohydrate supplementation decreased the intakes of DM from forage (P<0.10). The nitrogenous compounds supplementation increased the digestibility coefficients of DM and NDFom(n) (P<0.10). The carbohydrate supplement caused a lower intake of digested NDF (P<0.10). There was interaction between nitrogenous compounds and carbohydrates (P<0.10) on urinary excretions of total and urea nitrogen, on urea nitrogen contents in serum, or ammonia nitrogen in rumen fluid, and on efficiency of microbial synthesis. The supplementation with nitrogenous compounds and carbohydrates together increases the nitrogen assimilation in the rumen. The protein supplementation increased 14.8% the NDF weighted degradation rate. The estimate of this parameter was decreased 32.5% when carbohydrates were supplemented. The evaluation of weighted rumen dynamics rate indicated that carbohydrate supplementation causes negative effects on forage NDF utilization.

ASSUNTO(S)

suplementação avaliacao de alimentos para animais starch supplementation uréia urea amido

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