Influence of Variable Rumen Degradation Constants Determined by Different Models on Effective Degradability of Dry Matter and Nitrogen

Rumen degradation rate constants and effective degradabilities (ED) of DM and N were determined in leucaena, poplar and wiilow tree forages by the in situ nylon bag ttehnique. The calculations were made for three different peak hours of fermentation according to three different models : i) assuming that the entire material is degraded in course of time, ii) taking into consideration only the potentially degradable Fraction, and iii) a modified model based on the combination of the former two. There was a wide variation in the degradation rate constants of both DM and N but the effective degradability was affected little. The degradability of N in forages was also corrected for bacterial N contaminatton of nylon bag residues. The results on ED of both DM and corrected N suggested that prolongation of the period of in situ rumen fermentation of forages in nylon bags beyond 48 h may not be necessary.