Degradabilidade ruminal in situ de vagens de faveira (Parkia platycephala Benth.) em diferentes tamanhos de partículas

Chemical composition, fermentative characteristics, and in situ ruminal degradability of elephant grass silage containing Parkia platycephala pod meal and urea

This study aimed to evaluate the effects of the addition of Parkia platycephala pod meal (PP) and urea on the chemical composition, fermentation characteristics, and in situ ruminal degradability of elephant grass silage. A completely randomized design with a 4 × 2 factorial arrangement was adopted, with four levels of pod meal (0, 10, 20, and 30%) and two levels of urea (0 and 1.5%) on as fed basis. The produced silages were evaluated in terms of dry matter (DM), crude protein (CP), mineral matter (MM), neutral detergent fiber (NDF), acid detergent fiber (ADF), hemicellulose, ammonia nitrogen, pH, short chain fatty acids, and in situ ruminal degradability. For the study of degradation, four Santa Ines rumen fistulated sheep, with average weight of 45 ± 2.5 kg were used. The association of the additives increased (p < 0.05) DM, CP, DM degradability, fractions a, b, and effective degradability at all passage rates (2, 5, and 8%/h) and reduced NDF and ADF contents. DM disappearance increased (p < 0.05) during the incubation time, especially for the silages containing the two additives. The interaction in the rumen environment is essential for microbial multiplication. Thus, the use of additives such as PP and urea contributed to the availability of digestible fractions of the feed and greater use by ruminal microorganisms. The association of Parkia platycephala with urea improves the fermentation characteristics, chemical composition, and degradability of elephant grass silage.

Mixed nonlinear models in ruminal in situ degradability trials

Abstract Classical methods of analysis of nonlinear models are widely used in studies of ruminal degradation kinetics. As this type of study involves repeated measurements in the same experimental unit, the use of mixed nonlinear models (MNLM) is proposed, in order to solve problems of heterogeneity of variances of the responses, correlation among repeated measurements and consequent lack of sphericity in the covariance matrix. The aims of this work are to present an evaluation of the applicability of MNLM in the estimation of parameters to describe the in situ ruminal degradation kinetics of the dry matter of Tifton 85 hay and to compare the results with those obtained from the usual analysis in two-phases. The steers used in the trial were fed diets composed of three different combinations of roughage and concentrate and two hays with different nutritional qualities. The proposed approach was proven as effective as the traditional one for estimating model parameters. However, it adequately models the correlation among the longitudinal data, which can affect the estimates obtained, the standard error associated with them and potentially change the results of the inferences. It is quite attractive when the research seeks to understand the behavior of the process of food degradation throughout the incubation times.

Valor nutritivo do capim-andropogon em quatro idades de rebrota em período chuvoso

Objetivou-se avaliar o efeito da idade após rebrota (35, 49, 63 e 77 dias) sobre a relação folha/colmo, composição bromatológica, produtividade e degradabilidade in situ do capim-andropogon (Andropogon gayanus Kunth.). Houve efeito linear crescente (P<0,01) dos dias de crescimento sobre os teores de MS e FDA na planta e de FDN e FDA nas folhas e decrescente para PB e MM na planta. Houve efeito quadrático (P<0,01) para teores de FDN na planta, PB nas folhas e relação folha/colmo. A produtividade foi influenciada (P<0,01), com acréscimo de 0,0388t de MS.ha-1 por dia de crescimento. A degradabilidade potencial da MS e FDN foram elevadas aos 35 dias após rebrota, nos três tempos de incubação, com decréscimos em função da elevação da idade de rebrota. Aos 35 e 63 dias após rebrota, verificou-se maior degradabilidade potencial da PB. A degradação efetiva da MS foi elevada aos 35 dias, enquanto para FDN maiores valores foram verificados aos 35 e menores aos 77 dias. O capim-andropogon, no intervalo de 35 a 49 dias após rebrota, apresenta maior degradabilidade potencial e degradação efetiva da matéria seca, proteína bruta e fibra em detergente neutro, decorrente da melhor relação folha/colmo associado ao menor teor de fibra, além de apresentar teor proteico 6 a 8%, suficiente à mantença de ruminantes.