SEMINAR: Plant Biology Research Seminar

Agriculture in particular ruminant livestock, is a major anthropogenic source of potent greenhouse gas, methane, where abundant gas is produced and expelled into the environment during fermentation of food in the animal gut. Annual forage legume Biserrula pelecinus L. (biserrula) act as an excellent bioactive plant to mitigate enteric methane production from ruminants. There is a critical need to progress knowledge on the nature of this anti-methanogenic effect, in particular how it might be influenced by various plant and environmental factors. The focus of my thesis was to investigate the mechanism(s) of the anti-methanogenic properties of biserrula and to understand how different types of plant stress (physiological and environmental) affect the activity of this pasture towards rumen microbes. The key findings are that the anti-methanogenic bioactivity of biserrula persists over time, and/or when mixed with another plant (subterranean clover), in vegetative and reproductive growth stages, and when the plant was defoliated or exposed to a gradient of soil phosphorus (P). It was also shown that the plant was targeting methanogens directly, as a significant reduction in total methanogen occurred without hampering key fermentation parameters in a continuous culture system. Chemical profiling indicated the presence of flavonoid glycosides as a major component of these fractions. One biserrula genotype showed lower anti-methanogenic bioactivity compared with other biserrula genotypes at all levels of P and also exhibited increase in anti-methanogenic bioactivity at higher P levels in the soil. Moreover, the physical damage of the plant via defoliation at the reproductive stage also slightly reduced anti-methanogenic bioactivity. While there was some genotype effect within biserrula for anti-methanogenic bioactivity in response to these stressors, this was small compared to the species effect (i.e. the comparison with subterranean clover). Overall, the research showed the effectiveness and consistency of the anti-methanogenic bioactivity of biserrula and the effect is reliant on specific chemical compounds within the plant that target rumen methanogens. Stresses imposed to the plant do not markedly reduce the potency of the anti-methanogenic bioactivity of biserrula. These results will help to develop the grazing strategies and potentially novel plant-based feed additives to manipulate enteric methane production.