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 kinetics of ruminant feeds. In principle, the technique is similar to other in vitro digestibility procedures using ground particulate substrates, anaerobic media and a rumen fluid inoculum. It differs, however, in that incubations are conducted in gas-tight culture bottles, thus enabling gases to accumulate in the head-space as the fermentation proceeds. A pressure transducer connected to a digital readout voltmeter and gas-tight syringe assembly is then used to measure and release the accumulated gas pressures from the incubating culture bottles. By repeating this gas-measurement, gas-release procedure at regular intervals during the fermentation, it is possible to construct gas accumulation profiles for feeds by summation of regression-corrected gas volumes. These profiles are then described using a recently derived growth function 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 respect to their in vitro fermentability.