In vitro estimation of rumen fermentable organic matter using rumen fluid and a cell free preparation of rumen fluid

Abstract

The amount of microbial protein leaving the rumen is considered as a function of the amount of rumen-fermentable organic matter (FOM) in the rumen. FOM can be calculated using tables, or estimated by in situ incubation, but both methods have some drawbacks. In vitro methods were therefore developed to estimate FOM, using fresh rumen fluid or a cell-free preparation of rumen fluid. Results were compared with the in situ method and a method using chemical feed composition. The in vitro methods gave a good prediction of the in situ estimation of FOM for the majority of feeds. For some feeds rich in starch or fat, the correlation was poor. Because no in vivo data of FOM were available, it could not be determined whether the in vitro or in situ methods gave false results. However, arguments suggest that the in situ method is not suitable for some feeds.