Suplementação nitrogenada ruminal e/ou abomasal em bovinos alimentados com forragem tropical

• Autor(a) principal: Rufino, Luana Marta de Almeida
• Data de Publicação: 2011
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/5702
• topic: Compostos nitrogenados; Suplementação; Balanço de nitrogênio; Nitrogen compounds; Supplementation; Nitrogen balance; CNPQ::CIENCIAS AGRARIAS::ZOOTECNIA::NUTRICAO E ALIMENTACAO ANIMAL

The objective of this work was to evaluate the effects of supplementation with nitrogenous compounds in the rumen and, or in the abomasum on intake, digestibility, rumen dynamics of fibrous compounds and on the parameters of nitrogenous compounds metabolism in cattle fed tropical forage. The experiment was carried out from June 2010 to February 2011. Four Nellore young bulls, averaging 227±11 kg body weight (BW) and fitted with rumen and abomasums canullaes, were used. The following treatments were evaluated: control (only forage), ruminal nitrogenous compounds supplementation (daily supply of 230 g of crude protein in the rumen), abomasal nitrogenous compounds supplementation (daily supply of 230 g of crude protein in the abomasum), and ruminal and abomasal nitrogenous compounds supplementation (daily supply of 230 g of protein, being 115 g in the rumen and 115 g in the abomasum). The basal diet consisted of Tifton 85 (Cynodon spp) hay, which presented average crude protein (CP) content of 78.4 g/kg of dry matter (DM). The experiment was implemented and analyzed according to a 4 x 4 Latin square design, balanced for residual effects, with four treatments, four animals and four experimental periods lasting 29 days each. The experimental periods consisted of three phases or sub-periods. At first one, it was evaluated the animal response in terms of intake without supplementation. In the second sub-period it was assessed the intensity of animal response in terms of changes in intake according to supplementation. In the third sub-period, it was supposed that animals were under a steady state with regard intake, digestibility and metabolism according to the treatments. From this assumption, it was evaluated the digestibility, the rumen dynamics of fibrous compounds, and the characteristic of the rumen and metabolism of nitrogenous compounds. There was no effect of the treatments (P>0.10) on voluntary intake of DM and neutral detergent fiber (NDF) during the first two experimental sub-periods. During the third sub-period, there was no effects of treatments (P>0.10) on forage or NDF intake. The CP intake was increased by supplementation (P<0.10) despite of supplementation site. The total digestibility coefficient of CP was increased (P<0.10) when supplement was supplied compared to control treatment, but no differences (P>0.10) among supplementation sites were detected. The ruminal digestibility of CP was higher (P<0.10) with ruminal supplementation compared to the control and ruminal/abomasal supplementation. These latter treatments propitiated higher estimates (P<0.10) of rumen digestibility of CP compared to abomasal supplementation. It must be emphasize that the ruminal digestibility coefficient of CP was positive for ruminal supplementation and negative for the other treatments. All treatments differed (P<0.10) with regard the intestinal digestibility of CP; being in decreasing order: abomasal supplementation, ruminal/abomasal supplementation, ruminal supplementation and control. There was effect of treatments (P<0.10) on the mass of CP digested in the intestine (IDP). The higher IDP was observed for abomasal supplementation compared with ruminal/abomasal supplementation and treatment control; the ruminal supplementation taken an intermediate position in the multiple comparison profile. The intestinal flow of microbial nitrogenous compounds and microbial efficiency did not differ among treatments (P>0.10). There was no effect (P>0.10) of treatments on the ruminal degradation and passage of NDF. Higher concentrations of rumen ammonia nitrogen (RAN; P<0.10) were observed for ruminal supplementation compared to the control and abomasal supplementation, which did not differ (P>0.10) each other. Ruminal/abomasal supplementation caused intermediate RAN concentrations. The concentration of serum urea nitrogen (SUN) was higher (P<0.10) for ruminal supplementation compared to ruminal/abomasal supplementation, which in turn was higher than the control (P<0.10). The average concentration of SUN obtained with abomasal supplementation was intermediary to the other supplementation forms and did not differ from both (P>0.10). The apparent nitrogenous compounds balance (NB) was increased (P<0.10) with the supply of supplement when compared to control treatment, regardless of the supplementation site. There were no differences (P>0.10) among treatments with regard to efficiency of nitrogen utilization. However, supplementation increased on average by 350% the efficient of use of absorbed nitrogen. The control treatment had higher (P<0.10) urinary excretion of 3-methyl histidine compared to treatments involving supplementation, which did not differ (P>0.10) each other. The supplementation of cattle fed tropical forage with nitrogenous compounds in the rumen and, or post-rumen causes similar increases in the retention and the efficiency of utilization of nitrogenous compounds. However, the metabolic mechanisms involved in the efficiency improvement seem to be different. These mechanisms are probably based on the increment of the ruminal pool of ammonia with the ruminal supplementation and in the increase of the mass of protein digested in the small intestine for the post-ruminal supplementation.