When it comes to sustainable livestock production, agribusiness news outlets are littered with articles about carbon capture, regenerative agriculture and feed supplements to reduce methane emissions from livestock. Asparagopsis seaweed has been in the spotlight for its potential to significantly reduce methane emissions from ruminants, but what is often not talked about is how methane emissions from cattle are measured. 

The push for R&D into methane reducing feed supplements

It is well established in literature (and now mass media) that ruminant livestock produce greenhouse gases (GHG).

Population growth and increasing demand for protein is putting pressure on the red meat industry to sustainably produce livestock products (OECD/ FAO, 2021).

With enteric fermentation representing the largest proportion of GHG emissions from ruminants, strategies such as feed supplements are gaining increasing attention as a mechanism for direct reduction in industry emissions.

Australia’s red meat industry has set an ambitious target to be carbon neutral by 2030, and has set the key milestone of making “livestock supplements available through commercial partners” by 2023 (Meat and Livestock Australia, 2020).

Figure 1: Estimated greenhouse gas emission sources from ruminants (FAO, 2019).

Measuring enteric methane emissions from livestock

Enteric methane emissions essentially refers to methane expelled by livestock by burping  

Microbes in the rumen break down feed and methane is released as a by-product via a process known as methanogenesis.

When testing the ability of feed supplements to inhibit methanogenesis, researchers can conduct experiments either in vivo or in vitro.

In vitro experiments

In vitro measurement occurs in laboratory settings in a controlled environment (Eske, 2020).

Experiments occur outside of the animal, so methane production is not being measured directly from livestock.

Specific scientific methods are used to measure GHG production, but essentially, ruminant fluid is extracted from cannulated livestock and is combined with the feed supplement extract under investigation to assess for any changes in microbial populations responsible for methanogenesis, alongside changes in gas production.

These are complex, controlled experiments involving tight incubation temperature controls and use of various scientific techniques and devices such as gas chromatographs (Bhatta et al., 2009).

Measuring enteric methane emissions in vivo

In contrast, in vivo experiments involve entire, living organisms (Eske, 2020).


So when it comes to measuring the effect of feed supplements for reducing enteric methane emissions, livestock will actually be fed the supplements and their emissions will be measured over time.

Often experiments measure other key variables such as live weight gain and milk production to assess productivity effects.

There are a few different techniques used throughout scientific literature, each with their own benefits and drawbacks (Min et al., 2020).

Examples of such techniques include:

  • The sulphur hexafluoride tracer technique
  • Respiration chambers
  • The Green Feed system- a turnkey system that measures gas fluxes from individual animals when they place their head into a chamber to eat feed (C-Lock, n.d.)

How many Australian farmers are using feed supplements?

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SOURCES

FAO. (2019). Five practical actions towards low-carbon livestock. Rome. ISBN 978-92-5-131985-7

OECD/FAO. (2021). OECD-FAO Agricultural Outlook 2021-2030.OECD Publishing, Paris. https://doi.org/10.1787/19428846-en.

Meat and Livestock Australia (2020). The Australian Red Meat Industry’s Carbon Neutral by 2030 Roadmap. Retrieved 15 August, 2021 from https://www.mla.com.au/research-and-development/Environment-sustainability/carbon-neutral-2030-rd/cn30/#

Eske, J. (2020, August 31). What is the difference between in vivo and in vitro?. Medical News Today. Retrieved 15 August, 2021 https://www.medicalnewstoday.com/articles/in-vivo-vs-in-vitro#in-vitro

C-Lock (n.d.). GreenFeed – Large Animal. Retrieved 15 August, 2021 https://www.c-lockinc.com/researchers/products/greenfeed-large-animals

Bhatta, R., Uyeno, Y., Tajima, K., Takenaka, A., Yabumoto, Y., Nonaka, I., . . . Kurihara, M. (2009). Difference in the nature of tannins on in vitro ruminal methane and volatile fatty acid production and on methanogenic archaea and protozoal populations. Journal of Dairy Science, 92(11), 5512-5522. doi:https://doi.org/10.3168/jds.2008-1441Min, B.R., Solaiman, S., Waldrip, H.M., Parker, D., Todd, R.W., Brauer, D.(2020). Dietary mitigation of enteric methane emissions from ruminants: A review of plant tannin mitigation options. Animal Nutrition 6, 231-246. https://doi.org/10.1016/j.aninu.2020.05.002