Methane (CH4) is a by-product in the digestion of plant material by all cattle and sheep. Effectively it is wasted feed material and energy that could otherwise be available for animal production. It is also a major greenhouse gas (14% of Australia's emissions). Beef cattle contribute 50% of these emissions. Many lipid containing feed materials are known to reduce methane emissions, as well as increasing productivity when used as supplementary feeds.
The purpose of this project is to investigate the impact of lipid containing feed additives on the suppression of methane emissions and improvements in the growth rate of steers fed a basal diet of tropical pastures.
A range of lipid supplements, Algamac 3050 (3, 5 and 7% oil inclusion in the diet),
Spirulina (3%), canola oil (5 and 7% inclusion) and safflower oil (3, 5 and 7% oil inclusion in the diet), were tested in vitro.
Algamac 3050 at all levels of inclusion reduced methane generation whilst appearing not to affect rumen microbial population dynamics, including the methanogen population. There were no differences in dry-matter digestion or the numbers of methanogens or methanogen population structure. All levels of Algamac inclusion had similar effects, suggesting that the mechanism that lowers methane with algal oils is different to that of other oils, which directly impacts on the microbial ecosystem at higher levels of inclusion.
Canola oil at 7% inclusion appears to only transiently reduce methane generation and would not appear to be a good candidate as a feed supplement for lowering methane emissions. The effectiveness of safflower inclusion is dose related. Safflower at 7% inclusion reduces methane generation significantly and at a constant level. The inclusion at 5% was not effective at reducing methane production.
A range of lipid containing supplements were tested in vivo in a feeding trial using Bos indicus cross steers. The supplements included Algamac, sunflower oil (due to the commercial unavailability of safflower oil) and whole cotton seed. All lipid supplements were included at a rate of 50g lipid/kgDM. Supplementation increased live-weight gain over an 11 week period. The highest gain was from whole cottonseed supplementation (15.7kg) followed by Algamac supplementation (12.1kg). Supplementation of Algamac and sunflower oil reduced methane emissions on a live-weight and dry matter intake basis by around 22% and 19.4% respectively. Using these functions there was no reduction in methane emissions per head with whole cottonseed supplementation, however, when calculating methane emissions as a function of average daily gain (ADG), both whole cottonseed and Algamac supplementation had a four-fold reduction in emissions.
Taking this reduction into account plus the fact that increasing live-weight would reduce the number of days to market, the overall reduction in methane emitted would be substantial. It is recommended the use of whole cottonseed and Algamac as a supplement to cattle fed a basal diet of tropical pastures due to its positive impact on live-weight gain, and the reduction in methane per kilogram of average daily gain, however there are supplement uptake issues that need to be overcome.