An in vitro procedure for the estimation of in vivo digestibility of roughage plant cell wall components in herbivores using mixed rumen microorganisms

The potentially indigestible plant cell wall components in representative samples of feedstuffs and animal feces (resp. a and b, expressed as a percentage of the neutral detergent residue, NDR) can be measured after incubation of these materials with mixed rumen microorganisms for several weeks at 40°C. From these values the percentage of NDR that was digested in the animal can be calculated. Similarly, the procedure can be used to estimate the digestibility of specific cell wall carbohydrates such as cellulose and hemicellulose after analysis of acid detergent fiber (ADF) and lignin.

The validity of this procedure was tested in digestion trials with ponies and wethers fed grass hay. The digestibility coefficients for NDR hemicellulose and cellulose determined with the in vitro procedure did not differ significantly from values obtanied with the conventional in vivo digestion trial.

The in vitro procedure has been applied to measure NDR digestibility in a variety of animals such as grazing geese and several species of exotic ruminants fed a mixed diet of hay and concentrates.