Livestock Research for Rural Development 33 (12) 2021 LRRD Search LRRD Misssion Guide for preparation of papers LRRD Newsletter

Citation of this paper

Reducing enteric methane emissions from ruminants by feeding yeast-fermented rice. A refinement of methodology practiced by rice farmers to make rice wine

T R Preston, R A Leng1 and María E Gómez Z2

Centro para la Investigación en Sistemas Sostenibles de Producción Agropecuaria (CIPAV), Carrera 25 No 6-62 Cali, Colombia
1 University of New England, Armidale, NSW, Australia
2 Cali, Colombia

The COP26 UN Climate Change Conference

The decisions made at this conference will have major influences on the survival of our civilization as we presently know it.

The major objective of this conference was to have all countries commit to take the necessary measures to arrive at zero emissions of greenhouses gases before or by the year 2050 (NetZero50). To those of us involved in livestock production research and extension our immediate goal It is the need to reduce emissions of Greenhouse Gases (GHG): carbon dioxide, methane and nitrous oxide and simultaneously increase carbon capture in soil deposits, as well as above-ground and underground biomass. There is a need to reduce the word’s emissions of methane from the many sources but particularly including that from enteric sources, since methane has very strong negative effect on global warming relative to carbon dioxide.

The implications of Net50Zero for the Republic of Ireland are reported as requiring that at “1.3 million cows would have to be culled” (Guardian On-line Newspaper, 11 November 2021).

The national cattle herd in the Irish Republic was 7.2 million in 2019 (CSO, Google Search, 2021) Reducing methane emissions from cattle by 20% would bring the same emissions benefits as reducing the national herd by 1.3 million animals.

Alternative ways of reaching Net50Zero are urgently needed.

Several technologies are available for reducing enteric methane emissions from ruminant animals. It is not our aim to discuss the different methods and approaches that have been put forward. We wish, however, to draw attention to research recently published in LRRD on the simple options that are available for reducing enteric methane emissions from ruminant livestock and at the same time improving livestock productivity.

The research which is summarized in an earlier issue of LRRD (Preston et al 2021a) shows how a technology used by farmers in South-East Asia to make rice “wine” can be modified to produce a supplement which fed at low levels (4% as diet dry matter) reduces enteric methane production by up to 20% with comparable benefits on livestock productivity.

The traditional “rice wine” technology produces an end product used directly into an animal’s diet to lower enteric methane generation (Figure 1). For this modified procedure we suggest the terminology is describe as “Yeast-fermented rice”.

Figure 1. Fermenting polished rice to make wine Figure 2. The byproduct from rice wine production

Whilst the research has been done locally and it is important to confirm these promising results with “yeast fermented rice” and to expand the research for alternatives. For example, "yeast-fermented cassava root” (Sangkhom et al 2020) gave a similar reduction in rumen methane as fermented polished rice in one experiment. Polished rice is a staple of the diet in tropical countries and it is a major challenge to develop an alternative that is competitive with rice on price and priority as a staple of the human diet.

We have shown that the byproduct from this fermentation process to be active in reducing the production of methane with related improvements in liveweight gain and feed conversion (Preston et al (2021a).

We have also demonstrated there is no need to distill the ethanol (which forms the basis of rice wine).

The advantage of rice as the raw material is its widespread availability. However, it is the basic feed resource of in particular the poor people in tropical developing countries, thus are distinct benefits to be gained by replacing polished rice with an ingredient which is of lower cost and less competitive with human nutrition.

The immediate need is to identify and test other sources of fermentable carbohydrates (feed stock) which are low in protein.

For those researchers who wish to participate in this research we shall be pleased to provide further details and advice as required.

We suggest the priorities are:

  1. To test on a wider scale that yeast fermented polished rice will reduce methane emissions and increase ruminant animal productivity.

  2. To test alternative substrates for the fermentation process.
Assessing methane reduction potential

This is done most efficiently in an in vitro rumen fermentation which simulates the actual diet fed to the animal with and without the proposed supplement (Preston et al2021b). The description of the system and the method of operation is available via the link Sangkhom in vitro.

Meters for direct measurement of methane are available but expensive (USD 3500). A low-cost alternative is a method developed by Fievez et al (2005). Measuring methane in the intact animal in feeding trials can be done with a “Laser” enabled meter but the price is USD 15 000).


Fievez V, Babayemi O J and Demeyer a D 2005 Estimation of direct and indirect gas production in syringes: A tool estimate short chain fatty acid production that requires minimal laboratory facilities Animal Feed Science and Technology 2005 123–124 (2005) 197–210

Preston T R, Leng R A, Garcia Y, Binh P T, Sangkhom I and Gomez M E 2021a. Yeast (Saccharomyces cerevisiae) fermentation of polished rice or cassava root produces a feed supplement with the capacity to modify rumen fermentation, reduce emissions of methane and improve growth rate and feed conversion. Livestock Research for Rural Development. Volume 33, Article #61.

Preston T R, Leng R A, Inthapanya S and Gomez M E 2021b The rumen in vitro incubation system as a tool for predicting the nutritive value of ruminant diets and the associated emissions of methane. Livestock Research for Rural Development. Volume 33, Article #74. Retrieved October 29, 2021, from

Sangkhom I, Preston T R, Ngoan L D and Phung L D 2020 Effect of yeast-fermented cassava root compared with yeast-fermented rice on methane production in an in vitro rumen incubation of ensiled cassava root, supplemented with urea and leaf meal from sweet or bitter varieties of cassava. Livestock Research for Rural Development. Volume 32, Article #194.