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

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Abstract
A comparison was made be-tween 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 2 to 3 times as high as those from animals that were fed roughage. Colony counts in the absence of roughage represented 57-73% of the microscopic counts; corresponding figures for the high roughage ration were only 3-12%. Isolates (85) from the 10-8 or 10-9 dilutions were divided into 5 well-defined groups by the acids they produced from glucose. These groups were further subdivided on the basis of morphological characteristics. Organisms from the high-roughage ration represented a variety of types, with butyric acid formers comprising about one-third of the cultures. The predominant bacteria from the rations without roughage converted glucose mainly to acetic, lactic, or succinic acids.