The Bacterial Flora of the Rumen of Healthy and Bloating Calves

Rumen samples from five healthy milk‐fed calves and one healthy calf given a milk‐replacer diet containing yeast protein had pH values of 6.5–8.0, total counts of ca. 10 10 /ml and viable counts of 10 8 ‐10 10 /ml. The facultatively and strictly anaerobic, and obligately aerobic, components of the floras were enumerated and identified. Similar tests performed on samples from two calves bloating on the yeast diet had pH values of 4.8 and 5.3, and although total and viable counts were of the same order as those from healthy calves, obligately aerobic bacteria were not detected and counts of lactobacilli were elevated. Infusion of the rumen of a calf with yeast diet caused a reduction in pH from 7.3–5.1 and an increase of at least 100‐fold in the numbers of organisms capable of forming copious gas from yeast diet. Results suggest that milk or milk‐replacer diet normally does not enter the rumen to any extent but when it does, due perhaps to poor palatability, bloat may ensue.