Effects of Diet, Time After Feeding, and Position Sampled on Numbers of Viable Bacteria in the Bovine Rumen

Abstract

The numbers of bacteria, estimated by colony counts, in samples of rumen digesta obtained from different positions in the rumen were determined at 1.0, 2.5, 5.5, and 10 hours after feeding four heifers at 12-hour intervals at the maintenance level of intake. Four rations: chopped alfalfa hay, the same hay ground and pelleted, the same hay plus equal weight of grain mixture, and hay crop silage from a different source were fed. Numbers were lowest at one hour and increased significantly between 1, 2.5, and 5.5 hours. Only when pellets were fed were the numbers at one hour not significantly lower from those ten hours after feeding. Numbers in the ventral rumen when animals were fed each of the rations were significantly lower (P < 0.01) at a given time than in the dorsal rumen. Numbers in the reticulum were essentially the same as those in the ventral rumen when hay or hay-grain was fed, but were higher (P < 0.01) when pellets were fed and lower (P <0.05) when silage was fed. The results suggest that grinding of hay has effects on the numbers of bacteria per unit weight of digesta passing on to the omasum. © 1968, American Dairy Science Association. All rights reserved.