Agribusiness News August 2024 – Sector Focus: Reducing Enteric Methane

Using plant extracts to reduce enteric methane

Identifying feeding strategies to reduce enteric methane emissions  is a rapidly growing area of research.

Inhibitors work by targeting pathways that are essential to methane formation or targeting enzymes that are found only in some methanogens (rumen archaea that produce methane).

Natural feed additives such as plant extracts, essential oils, and marine algae have been investigated for their naturally occurring bioactive ingredients and methane reducing properties.

Some plants produce secondary compounds that possess methane reducing properties.  However, due to the inherent variability of natural sources, this can present a challenge in determining or predicting efficacy.

Tannins

These are natural compounds found in plants.  Plants which contain higher tannin contents have a lower nutritional value.  They can be added to the diet by inclusion of the plant as a forage or as a plant extract.  Tannins bind with proteins in the rumen, therefore reducing the utilisation of protein by microbes.

Hydrolysable tannins tend to act by directly inhibiting rumen methanogens, while condensed tannins reduce methane production through inhibition of fibre digestion.  The average reduction in methane production (g/kg dry matter intake) from research is around 8% but is very variable.

Saponins

These are natural compounds found in plants and have a detergent-like quality.  Saponins selectively bind with the cell membranes of ruminal protozoa causing cell death.  Tea saponins appear to have potential in lowering methane, however, more long-term studies are required.

Essential oils

Essential oils are naturally occurring secondary metabolites and volatile components that possess anti-microbial properties.  The exact mode of action varies between different essential oils but includes disruption of cell membranes and inactivation of microbial enzymes.  These actions reduce either the total microbial population in the rumen or the activity of the microbial population thus reducing the production of CH₄.

Taking advantage of the unique composition among plants, some studies have used a blend of essential oils containing extracts from multiple plants.  The antimicrobial nature of a variety of essential oils may imply a greater capacity to modify rumen fermentation.  There are already commercially available essential oil-based blends marketed towards providing both improved efficiency as well as reducing methane.  However, they do not currently have approval as a feed additive for methane reduction.

Marine algae

Seaweed is another natural resource that has emerged as an animal feed ingredient with the potential to reduce methane.  Red seaweed found in tropical marine waters has shown a promising reduction in methane.

A genus known as Asparagopsis, has a high content of the bioactive ingredient bromoform.  Bromoform reduces methane by inhibiting the enzyme involved in the final step of methane production.  Claims are up to 80% reduction of methane emissions, however there is limited evidence in the published literature to support this claim and particularly, a lack of evidence on high forage feeding and grazing systems.  Bromoform is also a potential carcinogen so more research is needed on the potential impact on animal and human health.

There are a number of consortiums also researching UK native seaweed supplements.  At the BSAS conference earlier this year, Frances Titterington from the Agri-Food and Bioscience Institute in Northern Ireland presented findings from their study on a native brown seaweed species.  Although in the lab it had shown promising results to reduce methane by 10 – 15%; they did not find this to be the case when fed to finishing beef cattle.  They concluded this was likely due to the limitation of inclusion rate due to the high iodine content of the seaweed.

Outlook

In the UK, there is currently only one synthetic feed additive approved for methane reduction – Bovaer®.  M&S recently announced a collaboration with DSM, the company behind Bovaer®.  Morrisons is in partnership with Sea Forest, an Australian company utilising Asparagopsis seaweed and Queen’s University Belfast who are trialling UK and Irish seaweeds.  As retailers continue to invest in this area of research in an effort to reach their ambition to achieve net zero agriculture emissions from their suppliers, it is likely we will see more of these products being made available.

Mary Young, mary.young@sac.co.uk

 

Image credit: Derek Keats @flickr