A Comparison of Microbial Cellulase and Live Cell Rumen Inoculum for Estimating In Vitro Digestibility of Range Grasses

James B. Koostra, Robert J. Kinucan, Delmar I. Davis


Three commercial-grade cellulase enzymes and a live cell rumen inoculum were used to compare in vitro digestible dry matter of five high cellulose grass species in advanced stages of maturity in the Trans-Pecos, Texas. Three prediction equations were developed to define the relationships between in vitro rumen inoculum techniques and those using cellulase enzymes. All microbial cellulase techniques reliably estimated digestibility, although the rumen inoculum provided a greater extent of digestibility (P < 0.01) than the cellulases. Different grass species exhibited varied levels of digestibility (P < 0.01). Prediction equations between the rumen fluid and cellulase techniques were well correlated (1= 0.69 to 0.81) and highly significant (P < 0.01). These data suggest that enzyme digestibility estimates are effective and may be accurate predictors of live cell dry matter digestibility of range grasses consumed by ruminants.


alkali sacaton; Arizona cottontop; blue grama; IVDDM; Johnsongrass; sideoats grama; Trans-Pecos

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