Ruminal kinetics of the fibrous fraction of ruminant roughages

Abstract

The objectives of the present work were to characterize and determine the estimates of the parameters relating to  the kinetics of ruminal degradation of neutral detergent fiber (NDF) in hays from forest pasture, the jujube plant, mororo, oats and Tifton 85, and silages from corn, sorghum and forage cactus. The bromatologic-chemical composition, the degradation coefficients and the effect of ruminal fill of the NDF, were all determined. The bromatologic-chemical characteristics of the feeds under evaluation displayed variations in their nutritional components. The potentially degradable insoluble fraction of the NDF, corresponding to the B2 fraction of the studied feeds, showed variable deterioration. Hays from forest pasture, the jujube plant and mororo showed lower values for the potentially degradable fraction. The silages from corn and sorghum showed a small variation in the potentially degradable fraction and in the indigestible fraction, as well as in the degradation rate of the potentially digestible NDF. The highest total retention time was observed for forest pasture, the jujube plant and mororo followed by the silages, with the lowest values for this variable found in the hays from oats and Tifton 85. Forages, evaluated from semiarid regions (forest pasture, jujube and mororo), may limit dry-matter intake due to lower values of the potentially degradable fraction and higher values of the indigestible fraction. The effect of NDF ruminal fill is determined by the integration of various fiber characteristics. Thus the same restrictive inferences on physical intake cannot be made for any and all sources of fiber.