In vivo digestibility of cell-wall polysaccharides of Setaria splendida and Lolium perenne dv. Kangaroo Valley.

Abstract

A tropical and a temperate grass (S. splendida and L. perenne cv. Kangaroo Valley respectively) were cut at a young stage of regrowth and fed to sheep in pens. Although the fresh plants were chemically very similar, the apparent digestibility of the S. splendida (61'4%) was much lower than that of the ryegrass (76'1 %). Analyses of the faeces showed that the hemicellulose and cellulose in each grass were digested to a similar extent, but between species, the cell-wall polysaccharides of ryegrass were digested to a much greater extent than those of S. splendida (c. 79 and 49% respectively). Notable differences between the grasses were the hemicellulose A content of the faeces from sheep fed S. splendida, which was greater than that present in the fresh plant material, and the ryegrass hemicellulose B, which had a much higher arabinose content than that of S. splendida. Glucose and galactose, which were present in the fresh plant hemicelluloses, were absent in the faeces. The differences in apparent digestibility between the two grasses could not be explained in terms of their cell-wall polysaccharide content, but resulted from differential digestion of both the hemicellulose and cellulose of each species.