Ruminal Flora Studies in the Sheep

Abstract

A method of obtaining ruminal samples for the investigation of the ''free'' micro-organisms of the sheep''s rumen by means of a stomach-tube is described. Though the total numbers of organisms per unit volume obtained in this way were less than in samples taken directly from whole-rumen contents, the correlation between the counts for the 2 series of samples and the constancy of the difference are considered to justify the stomach-tube method as a means of assessing changes in the number of micro-organisms in the rumen. In a feeding trial designed to determine the effects of varying intakes of protein on the number of ruminal micro-organisms, 5 sheep were fed 5 levels of protein derived from casein and oaten hay, the levels of protein consumed being approx. 3, 6, 9, 10, and 12% of the dry matter of the ration, an extremely high correlation (r= + 0.98) was found between the levels of intake of protein and the numbers of micro-organisms in the rumen; evidently the number of organisms was detd. by the protein intake. The regressions for the numbers of organisms against protein N indicate that a relatively constant proportion of the ingested protein (of the order of 50%) was converted to bacterial protein. These findings, together with the ''true'' digestibility and biological value of the protein of each ration, are discussed in relation to protein metabolism in the ruminant.