Feed supplements to reduce methane emissions?

Ainslie Macdonald – Research Fellow at the PICCC (Primary Industries Climate Challenges Centre), The University of Melbourne

Methane is the main greenhouse gas produced in grazing systems. Ruminant livestock (cattle, sheep and goats) have microbes in their rumen called methanogens. These microbes produce methane (from the fermentation of feed) that is then belched out. Feed with lower digestibility produces more methane than higher quality feeds. Belched methane represents energy lost from your production system that might otherwise be converted to the milk, meat or fibre that generates income. Methane is a major inefficiency in animal production systems with 2–12 per cent of the gross energy intake lost as methane. This energy loss has been calculated as the equivalent of up to 55 to 60 days of grazing intake for ewes and steers and 40 days for dairy cows. Emissions from methane need to be reduced in the move to carbon-neutral agriculture and new feed additives that inhibit methane production may assist in achieving a carbon-neutral future.

Bovaer® and Asparagopsis are two different feed additives that are currently available for commercial use in Australian cattle feedlots to inhibit methanogens from producing methane.

Bovaer®, also known as 3-NOP, is manufactured by DSM Nutrition and replaces an enzyme required during the last stage of methane production, preventing methane from being produced. Bovaer® is metabolised within a few hours of consumption into compounds already found in livestock and is safely excreted with no negative effect on animals or environments. The introduction of 3-NOP during the last stage of methane production prevents the supplement from affecting any other aspect of digestion that may reduce productivity.

DSM recommends about 1 g a day for cattle to reduce methane emissions by 30 per cent, well below the maximum dosage recommended by the European Union EFSA Panel (88–100 mg 3-NOP/ kg of DMI). However, the potential for abatement could be higher in Australian diets. The only Australian study published on Bovaer® shows that a wheat-based diet high in oil can, in conjunction with Bovaer® reduce methane emissions by an average of 78 per cent in cattle. Currently, DSM is building a factory in Scotland to meet future global demand and trialling delivery methods for grazing animals including lick blocks and pellets, with the aim to roll out Bovaer® to ruminants in grazing systems to meet 2030 emission reduction targets. Some work has also begun on early life programming which aims to change the microbes in the rumen during ruminants’ early life. Calves fed 3 mg of 3-NOP/kg BW mixed in water for their first 14 weeks of life sustained reductions in methane emissions for a year post-weaning. The production and transportation of Bovaer® will approximately emit 34–52 kg of CO₂ for every kg of Bovaer® produced but will prevent 138.6 kg of methane, which has a global warming potential 82 times higher than CO₂ (over a 20-year period) from being emitted.

Asparagopsis amarta and Asparagopsis taxiformis, are two red macroalgae species native to Australia’s temperate and tropical coastline respectively. FutureFeed licenses companies to produce and distribute Asparagopsis as a feed additive. Asparagopsis naturally stores halogenated compounds capable of inhibiting methane production in its glands as a defence mechanism. The primary active compound in Asparagopsis is bromoform, which reacts with vitamin B12 to interfere with the enzyme required during the last stage of methane production.

The inclusion of Asparagopsis at 0.2 per cent of organic matter has been shown to nearly eliminate methane emissions in cattle in one study. However, post-mortem examinations on 10 sheep showed degeneration of the rumen surface from the inclusion of Asparagopsis at 0.5 percent of organic matter and above, suggesting that Asparagopsis may damage the digestive system of ruminants and doses should ensure to balance animal health and methane reductions. Asparagopsis can be produced in both open-ocean or land farming systems, but the large-scale production of Asparagopsis may reduce the biodiversity of marine ecosystems and increase ozone depletion by 0.18–0.48 per cent. Asparagopsis must also be harvested, processed, and stored in a specific way to prevent the loss of bromoform. Currently, the best way to process the macroalgae is in an emulsion of Asparagopsis in oil. Not only does this preserve the most important ingredient, but through a different process, the oil is able to further inhibit methane production, reducing methane with less bromoform.

There has been only one study on feedlot sheep for both Bovaer® and Asparagopsis. The first study on sheep observed that nine Segureña sheep (a Spanish breed) had an average 17.38 per cent reduction in methane emissions when fed 100 mg of Bovaer® daily. The second study on 28 Merino-cross wethers fed dried Asparagopsis at 0.5; 1; 2; and 3 per cent of organic matter on average had 15, 52, 62 and 81 per cent reductions in methane emissions respectively. Initially, there was hope that supplements would convert the energy normally consumed by methane production to increases in animal productivity, with the expectation that supplements could offset their costs through increases in meat or milk production. To date, there is no consistent evidence that either Bovaer® or Asparagopsis will increase the productivity of animals. To be competitive and viable, supplements must be cheaper than the cost of continuing to emit greenhouse gas emissions. If Australian farmers can successfully use either product to significantly reduce emissions, this would be easier and cheaper than offsetting methane emissions in the long term. This could result in farmers accessing premium markets for products both domestically and internationally.

This article has summarised the current knowledge on these two products. It is important to note that there is significant research occurring around the world and in Australia to validate findings and address the need for practical methods to administer these products in grazing systems.

Infographic produced by DSM Nutrition to summarise the effectiveness of Bovaer®.

Asparagopsis armata in Granada, (Southern Spain) at 5-m depth

Feed supplements to reduce methane emissions?

Further reading