Rumen Microbial Yield from Sheep Genetically Different for Fleece Weight

Abstract

The supply of sulphur amino acids is a major determinant of wool growth rate (Reis and Schinckel, 1963). In grazing animals, absorbed sulphur amino acids are largely microbial in origin due to extensive proteolysis of dietary proteins in the rumen. Hence it is the yield of microbial protein that governs the rate of wool growth. On this basis it seemed plausible that some of the genetic variation in clean fleece weight associated with divergent selection, may reflect correlated changes in rumen function which have resulted in differences in the yield of microbial protein. The aim of this experiment was to determine whether animals from the Trangie selection lines (Dun, 1958) selected either for (F+) or against (F-) clean fleece weight since 1951, differed in a yield of microbial protein from the rumen. A more detailed description of results will be presented separately.