Carbohydrate fractionation and kinetic of the neutral detergent fiber in vitro degradation of the extrusa from grazing cattle

[摘要] - The objectives of the present work were to characterizate and determinate the parameters estimates related to the ruminal degradation kinetics of the carbohydrates in extrusa samples from animals maintained in a natural pasture of the Zona da Mata (MG) region, during the rainy and dry seasons of the year. To obtain representative samples, four esophageal fistulated steers were used in two experimental periods during the rainy season, and three of these animals were used in two experimental periods during the dry season, in the year of 1996. The carbohydrate fractionation according to the Cornell system was done, and the neutral detergent fiber (NDF) degradation rates were obtained from the in vitro degradation profiles of this component. The potentially degradable (B2) and undegradable (C) fractions of NDF corrected for protein and ash, the dynamic lag rates, the degradations rates, and the specific growth rates of microorganism upon fraction B2 were obtained, as well as the degradability coefficients and the rumen fill effect of NDF. As a result, it was possible to observe that the nonstructural carbohydrates comprised a minor fraction of the total carbohydrates in the pasture samples in both seasons. The structural carbohydrates were responsible by the total carbohydrate increase in the extrusa from the rainy to the dry season; nevertheless, due to the C fraction increase and to the lower specific microorganism growth rates during the dry season, it was noticeable the reduction of the extrusa NDF degradability and its increased rumen fill effect.

[学科分类] 兽医学

[关键词] ruminants;structural and non-structural carbohydrates;tropical pastures     IntroduçãoOs carboidratos compreendem os grupos de compostos que encerram as substâncias orgânicas mais abundantes da biosfera; além disso;constituem a principal fonte de energia para os primeiros níveis tróficos da teia alimentar (LEHNINGER et al