Measuring methane emission of ruminants by in vitro and in vivo techniques

Abstract

One of the problems our planet faces today is global warming due to the augmentation of the greenhouse effect which arises from accumulating gases that trap heat in the atmosphere. Methane is considered the second most problematic greenhouse gas emitted from anthropogenic sources (23) and its role in the destruction of the stratospheric ozone layer (17) is uncontested. Worldwide, approximately 81 Tg methane per year are emitted from the gastrointestinal tract of domestic ruminants and an additional 7 Tg of methane per year originate from the manure of these animals (7). Related to total anthropogenic methane emission, this means that domestic ruminants are responsible for 25% of total anthropogenic methane emission (9). Methane production in the rumen not only represents an ecological but also an economic problem. It was estimated that methane formation during fermentation represents a loss of 7-10% of the ruminant's gross energy intake (15), depending on the level of feed intake, diet composition and apparent digestibility of dietary energy. According to Johnson and Johnson (8), cattle can produce 250 to 500 L of methane per day. There is still a great lack of quantitative data on the efficacy of mitigation strategies, particularly in tropical regions where a very high proportion of domestic ruminants are kept, due to the difficulties in measuring ruminal methanogenesis in conjunction with variations in feeding. Therefore, the purpose of the present chapter is to describe extensively different techniques suitable for quantitative measurement of methane emission from ruminants. These in vitro and in vivo techniques allow the estimation of the efficiency of strategies in mitigating ruminal methane formation. © 2007 IAEA.