Effect of Sampling Site on Protozoa and Fermentation End Products in the Rumen of Dairy Cows

Three ruminally cannulated Holstein cows fed a diet containing 55% corn silage and 45% concentrate (DM basis) were used to compare rumen contents obtained from three sampling sites in the rumen. Rumen contents were collected from the dorsal, ventral, and anterior sacs of the rumen prior to (0 h) and at 2, 4, and 8 h after the a.m. feeding. Strained and unstrained rumen contents were preserved for protozoa count. Volatile fatty acids, NI-I3 N, and pH analyses were performed on strained rumen contents. Total protozoa numbers (entodiniomorphs and holotrichs), VFA, and NH 3 N concentrations were higher and rumen pH lower in nnnen contents obtained from the dorsal sac than in rumen contents from ventral and anterior sacs; however, holotrich numbers were not affected by rumen sampling site. Numbers of protozoa in strained preparation of rumen contents were greater than those in unstrained rumen contents. Data from this study suggest that differences in concentration of protozoa among ruminal sampling sites are related to end products of microbial fermentation.