Comparison of laboratory methods for the prediction of in vitro dry matter digestibility in three maturing grasses

Maturing reed canary grass, Russian wild rye, and smooth bromegrass were freeze-dried and ground. Samples were analyzed gravimetrically for detergent fiber components and cell wall constituents by using spectrophotometric and gas-liquid chromatographic assays. The relationship between cell wall composition and in vitro dry matter digestibility (IVDMD) was investigated by using regression methods. Acid detergent fiber and acid detergent lignin were the best single parameters for predicting IVDMD. However multiple linear regression equations utilizing the monomeric constituents of plant cell wall polysaccharides, lignin and silica, provided the best estimates of IVDMD. The arabinose:xylose ratio and galactose content may reflect the importance of hemicellulose polymer branching on the digestibility of forages