An automated system for measuring gas production from forages inoculated with rumen fluid and its use in determining the effect of enzymes on grass silage

This paper describes an automated system that has been developed to measure the production of fermentation gas from ruminant livestock feeds inoculated with rumen fluid. The design of the apparatus and its method of use enables gas production to be determined from fresh, unprocessed plant material, as well as the more commonly used ground, particulate substrates, thus representing a closer simulation of forages consumed in vivo. The system consists of 48×140 ml bottles containing 100 ml buffered rumen fluid and 1 g of test substrate. Gas is produced as a consequence of the fermentation of the substrate. Gas, accumulating in the head-space of bottles, is released automatically, by use of pressure sensitive switches and solenoid valves, when a pre-determined pressure is reached. This prevents any build up of pressure in the fermentation bottle, which can affect the behaviour of the gas and the fermentation process. Gas accumulation profiles are produced as the fermentation proceeds and give information on forage digestibility and fermentation kinetics. In this paper, we describe the principles of the gas production technique and provide examples of how the automated system has been used in the evaluation of forages for ruminants. The results obtained show that the automated system is a useful tool for the determination of fermentation kinetics of ruminant feeds. It is simple to use and is considerably less labour intensive than manual gas measurement techniques.