Composição bromatológica e degradabilidade, através da técnica de produção de gás, de quatro gramíneas tropicais submetidas a corte em diferentes idades

Abstract

The most of the beef and dairy cattle in Brazil is reared under extensive conditions where the pastures represent the most important source of nutrients. For this reason the understanding of the ruminal digestion is necessary to enhance the utilization of the pastures by the animais. In ruminant production, the roughages are the cheapest source of nutrients, especially when high productivity and adapted pastures are used. The carbohydrates represent the main source of the energy for the animals. The carbohydrate fragmentation of the feed is necessary for the identification and understanding of the process that occurs at the digestive tract. The knowledge of the digestibility of the roughage is important to reach the optimum fermentation and appropriate balance of the rations. Chemical composition, degradability by the gas production technique and carbohydrate fragmentation were evaluated at the Animal Science Department of the Federal University of Lavras (UFLA), using CNCPS equations for four tropical grasses (3 varieties of Pennisetum purpureum Schum. and one of Panicum maximum Jacq.), harvested every 30 days along 360 days. The age affected by a directly form the chemical composition and degradability of DM, NDF and NDS. DM, NDF, ADF, lignin and silic had increases in their contents; CP, EE, ashes and TDN showed decreases in their quantities. Gas production decreased for DM and NDS with the age increase of the plants and, consequently, decrease of the dry matter degradability. By the regression equations of the analyzed nutrients its possible to estimate the quality of tropical grasses according of its age.