Methane emissions from beef cattle can be reduced – BCBC Telford

In a bid to help reduce greenhouse gas emissions from livestock businesses, Rainer Roehe, Professor of Animal Genetics and Microbiome at Scotland's Rural College (SRUC), told delegates attending the British Cattle Breeding Conference, in Telford that such technology could be available in the next four or five years.

"When rumen microbiome-driven breeding is used intensively for methane mitigation in a cattle population, data from experiments carried out at the SRUC Beef Research Centre, predict a reduction in methane emissions of up to 17% per generation.

"The microbiome-driven breeding strategy uses genomic selection to estimate the breeding values of methane emissions and could therefore result in a reduction of the generation internal to 2.5 years and thus result in an annual reduction in methane emissions by up to 7% per year."

While the use of such technology requires further research, Professor Roehe said previous trials – based on beef cattle of the same trial, breed and fed the same diet – showed large differences in methane emissions between these cattle which is hugely encouraging for breeding low methane emitting cattle.

In a previous study, he said that significant differences had been found between sire progeny groups in methane emissions indicating that there are bulls inheriting low methane emissions. A recent study based on an SRUC population of Aberdeen Angus and Limousin rotational crosses, Charolais crosses and Luing, revealed a heritability of 0.33 for methane emissions which is similar to that of growth rates and feed efficiency, indicating that selection for methane emissions will be as successful as those traits, most likely even higher due to the large difference in methane emissions between animals within breed.

Such trials in the SRUC's GreenCow individual respiration chambers – the gold-standard for measuring methane emissions from ruminants – are however extremely costly and instead, Professor Roehe pointed out that concentrating trials on the microbial ecosystem, or rumen microbiome within individual cattle had proved more cost effective in estimating methane emissions.

The microbial ecosystem within cattle – essential to enable rumen enzymes to convert indigestible fibrous grasses into absorbable nutrients – produces hydrogen during microbial conversion of feed, which in turn results in the by-product methane, which is expelled through mouth and nose. Identifying the microbiome biomarkers for estimation of methane emissions, is a direct consequence of the microbial metabolism in the rumen.

Research as collaboration of SRUC, Genus plc and the University of Edinburgh revealed that approximately 30% of the composition of the functional core microbiome is influenced by cattle genetics, with heritabilities ranging from 0.15 to 0.66. Similar ranges of heritabilities were reported for the abundances of the identified specific microbes in dairy cows in the range from 0.08 to 0.62.

Based on study results, SRUC proposed a selection index based on the abundances of the 30 most informative microbial genes to reduce methane emissions to be referred to as microbiome-driven breeding strategy, which in years to come will be able to be used when selecting AI sires.

The collaborative research has also shown that microbiome-driven breeding based on rumen microbial information genetically linked to the feed conversion ratio rumen microbial was highly efficient to improve feed conversion ratio by up to 15% per generation.

"Our research also suggests that microbiome-driven breeding and dietary intervention are additive mitigation strategies and therefore can be efficiently combined to reduce methane emissions from cattle," concluded the Professor.