Physiological Bases for Divergent Methane Production in Ruminants

Abstract

Reduction of enteric methane production in ruminants has been identified as a practical strategy to reduce greenhouse gas emissions from the agricultural sectors of Australia. Most approaches being considered for reducing enteric methanogenesis have focused on physical or chemical intervention to reduce methane production and their success is problematic, as most ruminant production systems in Australia are extensive. There have been frequent observations of divergent methane production in cattle and sheep, and if such differences were persistent and heritable, selective breeding for low methane production may be a practical way to reduce enteric methanogenesis by ruminant populations. It has not been directly established whether the observed divergent methane production is robust and persistent, or what mechanisms were underpinning this divergence. This thesis was designed to identify animals which were in the extremes of the range for methane production, test the persistence of this characteristic over time and across diets, and elucidate the mechanisms underlying this divergence.