<i>In sacco</i> kinetics disappearance of NDF of small and large particles of the rumen contents in grazing dairy cows

Abstract

In sacco degradation curves of NDF from small (SP) and large particles (LP) of rumen contents, collected in dairy cows before or after grazing, were compared. LP and SP were defi ned as ruminal particles retained, or passing a 1 mm-pore-sieve, respectively. Degradation curves were fi tted with a fi rst order kinetics model. SP, compared to LP, contained a lower proportion of digestible NDF. Fractional degradation rates of NDF were lower for SP than for LP after the meal, and were not different between SP and LP before the meal. These results questions about representations of SP and LP in the rumen models.