Eremophila glabra reduces methane production in sheep

[Truncated abstract] Ruminant methane (CH4) production is the major source of agriculture CH4 emission in Australia and mitigating its emission is a priority. Substituting bioactive plants to the diet can alter rumen fermentation and reduce enteric CH4 production. Eremophlia glabra Juss. (Scrophulariaceae), a native shrub, reduces CH4 production but also has general inhibitory effect on fermentation when used as the sole substrate in vitro. This general effect can be reduced by mixing E. glabra with other substrates. E. glabra is fully adapted to the Australian Mediterranean climate and has potential to be used as an alternative feed source for livestock during the 'feed gap' in summer and autumn. This thesis explores the use of E. glabra as one component of a mixed diet to achieve low CH4 production without reducing animal production in sheep. My research sought to (i) evaluate the potential of E. glabra as a natural CH4 inhibitor, (ii) assess the feasibility of using E. glabra in the diet of sheep, (iii) investigate the mechanisms of action behind the antimethanogenic bioactivity, and (iv) determine the effective fractions and compounds in E. glabra responsible for the antimethanogenic effects. In this thesis, I initially tested the antimethanogenic and general antimicrobial effects of E. glabra in short-term (24 h) and long-term (3 weeks) in vitro fermentation and subsequently in vivo. I then explored the components of E. glabra responsible for the bioactivity...