Inconsistencies in rumen methane production-effects of forage composition and animal genotype

Strategies for methane mitigation require a robust prediction of emissions from rumen function. The poor relationship with digestibility and gross chemical composition of diets demands an integrated evaluation of methanogenesis to include plant, animal, microbial and perhaps adaptation variables. Basic concepts of digestibility, rumen residence time, physical aspects of the diet including recalcitrance and rates of degradation may impact on methanogenesis. In addition to the impact of archaea on methanogenesis, other sources and sinks such as pectin and ammonia are likely to affect net methane production. The clear differences between individual animals in their microflora, digestion and performance have been masked when groups are used to evaluate treatments. Animal variation provides a key to methane mitigation and must be given greater priority in future research.