Computerized monitoring of gas production to measure forage digestion in vitro.

The techniques reported in this paper were developed to facilitate the study of the kinetics of forage digestion in vitro by measuring gas production. Fiber disappearance as a measure of the reaction rate has been replaced by the use of computerized pressure sensors to monitor the gaseous products (CO2, CH4) of microbial metabolism. The recording system described requires a computer, pressure sensors, an interface card, and appropriate software to monitor gas production continuously. Several variables, including sample size, inoculum size, vessel size, and type of pressure sensor, have been investigated to determine ranges within which gas production can be measured accurately, and the reproducibility of the results has been established. Because this technique uses small (100-mg) samples, a modified NDF method has been introduced that allows determination of extent of digestion at the end of an incubation in which gas production has been monitored. A strong linear relationship existed between NDF disappearance and gas production.