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Effect of Roughage in the Bovine Ration on Types of Bacteria in the Rumen¹

Department of Bacteriology, University of Wisconsin, Madison

ABSTRACT

A comparison was made between the numbers and types of bacteria present in large numbers (one hundred million or more per milliliter) in the rumen contents of cows fed large amounts of roughage (alfalfa hay) and of cows fed no roughage (grain concentrate plus alfalfa meal). Total direct microscopic counts from samples containing no roughage were two to three times as high as those from animals that were fed roughage. Colony counts in the absence of roughage represented 57 to 73% of the microscopic counts, whereas corresponding figures for the high roughage ration were only three to 12%. The results suggest that the predominant organisms in the high roughage material were unable to grow into visible colonies under the cultural conditions provided.

Isolates from the 10^–8 or 10^–9 dilutions were characterized by the acids they produced from glucose. Organisms from the high-roughage ration represented a variety of types, with butyric acid formers comprising about one-third of the cultures. The predominant organisms from the rations without roughage converted glucose mainly to acetic, lactic, or succinic acids.

¹ Published with the permission of the Director, Wisconsin Agricultural Experiment Station.

² Present address: Department of Veterinary Science and Bacteriology, University of Wyoming, Laramie, Wyoming.