In vitro gas measuring techniques for assessment of nutritional quality of feeds: a review

The close association between rumen fermentation and gas production has been recognised for over a century, but it is only since the 1940s that quantification techniques for measuring gas production have been evolved. The gas measuring technique has been widely used for evaluation of nutritive value of feeds. More recently, the upsurge of interest in the efficient utilisation of roughage diets has led to an increase in the use of this technique due to the advantage in studying fermentation kinetics. Gas measurement provides a useful data on digestion kinetics of both soluble and insoluble fractions of feedstuffs. This review describes the available in vitro gas measuring techniques used for feed evaluation with emphasis on assessing their relative advantages and disadvantages. Origin of gas, stoichiometry of gas production, and various areas for application of gas measurement in feed evaluation are discussed. Some important results obtained using gas measuring techniques have been highlighted, and the potential of gas techniques for tackling some interesting areas of research are presented. The need to consider substrate incorporation into microbial cells in gas measuring technique is pointed out.