Grain and artificial stimulation of the rumen change the abundance and diversity of methanogens and their association with ciliates
In Australia, there is pressure to reduce the amount of methane produced by ruminant livestock because they are the single largest source of methane emitted from anthropogenic sources, accounting for 70.7% of agricultural methane emissions. In addition, methane production represents a loss of gross energy intake to the animal. The organisms that are responsible for methane production in the animal gut are a distinct group of Archaea called methanogens. Methanogens occupy three different niches within the rumen. Some live freely in the rumen digesta (planktonic), others are attached to the outer surface of the rumen ciliates (ectosymbiotic), and some reside within the ciliates (endosymbiotic). The types and number of methanogens, as well as rumen ciliates and their symbiotic interactions, influence the amount of methane produced from the rumen. These factors in turn are affected by many factors, including diet and ruminal retention time. In this thesis, I tested the general hypothesis that increasing the amount of grain in the diet and reducing the retention time would affect the abundance and diversity of methanogens in their different niches, including their association with ruminal ciliates.
Decreasing the emission of methane from ruminant livestock is desirable both as a strategy to reduce global greenhouse gas emissions and as a means of improving the efficiency of utilisation of digested energy by the animal. Energy lost as methane is 2–15% of the gross energy intake by the animal. This research project will give a better understanding of the complex interactions between methanogens and protozoa in the rumen. This will provide new information that contributes to a better understanding of methanogenesis in the rumen - a central point in controlling methane emission from ruminants.