A SIMPLE GAS-PRODUCTION METHOD USING A PRESSURE TRANSDUCER TO DETERMINE THE FERMENTATION KINETICS OF RUMINANT FEEDS

This paper describes a simple yet sensitive laboratory procedure that was developed to provide detailed information on the fermentation kine tics of ruminant feeds. In principle, the technique is similar to othe r in vitro digestibility procedures using ground particulate substrate s, anaerobic media and a rumen fluid inoculum. It differs, however, in that incubations are conducted in gas-tight culture bottles, thus ena bling gases to accumulate in the head-space as the fermentation procee ds. A pressure transducer connected to a digital readout voltmeter and gas-tight syringe assembly is then used to measure and release the ac cumulated gas pressures from the incubating culture bottles. By repeat ing this gas-measurement, gas-release procedure at regular intervals d uring the fermentation, it is possible to construct gas accumulation p rofiles for feeds by summation of regression-corrected gas volumes. Th ese profiles are then described using a recently derived growth functi on developed to characterise gas production profiles. Results obtained establish the pressure transducer as a suitable tool for determining the fermentation kinetics of ruminant feeds and ranking them with resp ect to their in vitro fermentability.