Dinâmica de degradação in vitro da fibra em detergente neutro de capim-braquiária em função de suplementação com diferentes níveis e fontes de compostos nitrogenados

• Ano de defesa: 2008
• Autor(a) principal: Zorzi, Karina
• Orientador(a): Queiroz, Augusto César de
• Banca de defesa: Mâncio, Antonio Bento , Mantovani, Hilário Cuquetto
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Viçosa
• Programa de Pós-Graduação: Mestrado em Zootecnia
• Departamento: Genética e Melhoramento de Animais Domésticos; Nutrição e Alimentação Animal; Pastagens e Forragicul
• País: BR
• Palavras-chave em Português: Caseína; Uréia; Capim-braquiária
• Palavras-chave em Inglês: Casein; Urea; Brachiaria decumbens
• Área do conhecimento CNPq: CNPQ::CIENCIAS AGRARIAS::ZOOTECNIA::NUTRICAO E ALIMENTACAO ANIMAL
• Link de acesso: http://locus.ufv.br/handle/123456789/5575

Two experiments in vitro were carried out to evaluate the in vitro degradation dynamics of neutral detergent fiber (NDF) of high and low-quality tropical forage according to supplementation with different levels and sources of nitrogenous compounds. In the two experiments casein was used as true protein source and the mixture urea: ammonium sulfate (U:AS, 9:1) was used as non-protein nitrogen source. At the first experiment, it was evaluated the in vitro degradation dynamics of NDF of high-quality tropical forage according to supplementation with nitrogenous compounds. A sample of signal grass, taken from a pasture during rainy season, was used as basal forage. Three treatments were defined by the levels of casein in final incubation solution: 0.5, 1.0 and 2.0 mg of casein/mL. The U:AS was included in the medium to form another three treatments, such the protein equivalents were the same that defined for casein supplementation. A treatment containing only forage was used as a control. The treatments were evaluated by an in vitro incubation procedure. The incubation times were: 0, 3, 6, 9, 12, 24, 36, 48, 72 and 96 hours. The incubation procedure was repeated four times. The incubation residues were evaluated for NDF, followed by the adjustment of a logistic non-linear model. The casein supplementation at the level of 0.5 mg/mL increased the degradation rate of potentially degradable NDF (kpdNDF) (+1.1%). However, supplementation with 1.0 and 2.0 mg/mL decreased the estimates of this parameter compared to control treatment (-6.4 and -9.1%, respectively). On the other hand, supplementation with urea caused a average increment of 7.6% on kpdNDF estimates. The concentration of ammonia nitrogen (AN) was higher with the supplementation. However, the urea supplementation, at the same levels of casein supplementation, produced higher AN levels in the incubation medium. At the second experiment, it was evaluated the in vitro degradation dynamics of NDF of low- quality tropical forage according to supplementation with nitrogenous compounds at different rations true protein:non-protein nitrogen. The experimental materials and procedures were such as in the first experiment, however a sample of signal grass taken from a pasture during dry season was used as basal forage. The incubation procedure was repeated three times. The reference treatment was defined through addition of casein in the incubation medium, such that the crude protein (CP) level of the basal forage was raised to 8.0%, as dry matter basis. In this way, the treatments were defined from fractional replacement of CP from casein by CP from U:AS (0, 1/3, 2/3 and 1). A treatment containing only forage was used as a control. The protein supplementation increased from 56.8 to 96.0% the kpdNDF compared to control treatment. At same time, the supplementation reduced the discrete lag time (-4.5 to -7.4 hours). The total replacement of casein by urea caused an increase of 15.9% on kpdNDF. However, the evaluation of replacement profile indicated that maximum estimates of degradation rate and microbial growing were obtained on 2/3 U:AS: 1/3 casein ratio.