Cellulose Digestion In Vitro as a Measure of the Digestibility of Forage Cellulose in Ruminants

The digestibility of the cellulose in seven grass hays and six legume hays was determined by an in vitro rumen technique using inocula obtained from a steer, and in digestion trials with sheep. No significant difference was observed between results obtained in vitro and in vivo with grass hays, but, in some of the legume hays, cellulose digestibilities, as measured by the two methods, were significantly different. Results obtained with the in vitro technique showed good reproducibility and, in general, variances were less than those calculated for the corresponding sheep trial data. In an experiment in which different forages were fed to a steer used as a source of inoculum, the digestibility in vitro of the cellulose in these forages was not affected by the type of forage fed the steer. Little difference was noted when cellulose digestion was measured using strained rumen juice, a phosphate buffer extract of pressed rumen contents or resuspended ruminal microorganisms as inoculum. Possible use of the in vitro technique as a tool in the evaluation of the nutritive value of forages is indicated.