Hydrolysis of the cell-wall carbohydrates of grasses by carbohydrases in relation to voluntary intake by sheep

Abstract

SUMMARY: The relationship between the voluntary dry-matter intake of grasses and theirin vitrodigestibility (DOMD), chemical composition and susceptibility to enzymic hydrolysis was examined in two experiments. The grasses were artificially dried and represented a range of species and varieties cut at various growth stages.In both experiments some 70% of the observed variation in intake could be attributed to differences inin vitrodigestibility between the grasses and between the growth stages when harvested. Estimations of acid detergent fibre, pepsin solubility and cellulose generally accounted for less than 70% of the variation in intake.The enzyme digestion techniques, on the other hand, accounted for up to 79% of the variation. The content of enzymically unhydrolysable cell wall gave the highest correlation with voluntary intake (r= −0·88 and −0·89, residual standard deviation 5·5 and 6·2, for the two experiments).It is concluded that simplified techniques based on cellulase digestion of plant material may be advantageously applied to breeding programmes with the expectation of identifying material high in digestibility and with good intake characteristics.