Abstract
The fermentation products and bacterial population in the rumen were examined in an experiment designed as a 5×5 Latin square, with five Holstein heifers fed five rations differing in ratios of rolled barley to hay (1:0, 3:1, 1:1, 1:3, and 0:1). The proportion of volatile fatty acids (VFA) in the rumen changed drastically when the percentage of barley exceeded 75%. The total and viable counts of rumen bacteria were higher with a high-barley diet. Selenomonas ruminantium, anaerobic lactobacilli, Peptostreptococcus, and Bifidobacterium were most prevalent in the rumen of heifers fed an all-barley diet. Succinivibrio dextrinosolvens was most frequently isolated from animals fed a ratio of 3:1 barley to hay. On the other hand, Butyrivibrio, Ruminococcus, and Bacteroides ruminicola were the most numerous of the bacteria from heifers fed a high proportion of hay. Also, the relationship between the bacteria dominant with each ration and their activities are discussed.
