Prediction of the digestibility of ruminant feeds from their solubility in enzyme solutions

The solubility of 24 diets containing grain and 23 forages was measured in solutions of either cellulase, pepsin or amylase. Sequential incubations in pepsin and cellulase (from Aspergillus niger) yielded solubility values which were significantly correlated with the dry matter digestibility in vivo of the diets containing grain (r = 0.85) and the forages (r = 0.82). When cellulase from Trichoderma viride was used instead of the cellulase from Aspergillus niger, the correlation was lower for the feeds containing grain (r = 0.60) but not for the forages (r = 0.84). The former method was comparable in accuracy to the two-stage technique for measuring digestibility in vitro with rumen fluid and pepsin, for which correlation coefficients of 0.89 and 0.83 were observed for the diets containing grain and the forages, respectively.