Each year, a single cow can belch about 200 pounds of methane. The powerful greenhouse gas is 27 times more potent at trapping heat in the atmosphere than carbon dioxide. For decades, scientists and farmers have tried to find ways to reduce methane without stunting the animal’s growth or productivity. 

Recent research at University of California, Davis, has shown that feeding cows red seaweed can dramatically cut the amount of methane that is produced and released into the environment. Until now, however, scientists did not fully understand how red seaweed changes the interactions among the thousands of microbes in the cow’s gut, or rumen. 

A new collaborative study by researchers at UC Davis, the University of California, Berkeley, and the Innovative Genomics Institute, or IGI, sheds light on that process and reveals which microbes in the cow’s gut might help reduce methane. The new insights bring the multidisciplinary team, composed of microbiologists, animal and computer scientists, closer to engineering the gut microbes of cows to produce less methane, offering a long-term solution that would not depend on seaweed feed additives. The study was published in Microbiome.

Seaweed transforms the cow gut

Scientists have previously shown that red seaweed of the genus Asparagopsis blocked a key enzyme found in methane-producing microbes in the cow’s gut. In the current study, researchers discovered that seaweed turned certain microbial genes on and off, a sign that these genes play a key role in how red seaweed helps cut methane from cows. As these genes switched on and off in the cow’s gut, hydrogen briefly built up. The team also identified a rumen bacterium that belongs to the genus Duodenibacillus that can use some of the hydrogen. 

“That’s important because too much hydrogen can lead to acidosis in the rumen, which can harm the animal,” said project leader and corresponding author Matthias Hess, a microbiologist and professor in the UC Davis Department of Animal Science and an IGI investigator. “Instead, this organism uses the hydrogen and converts it to succinate, a compound the animal can eventually use to make protein.”

Hess said the findings could open the door to engineering communities of hydrogen-hungry microbes that might outcompete methane-producing microbes.

“Hydrogen is a key energy source in the rumen, specifically for methane-producing microbes," said principal investigator Spencer Diamond, with the IGI. “This study helps us better understand how other microbes that naturally occur in the rumen can divert this hydrogen away from methanogens and towards bacteria that may make animals more efficient.” 

Scientists extracted fluid from the rumens of eight cows: four that were fed a regular diet and four that were also given a seaweed additive for 14 days. Cows that ate the seaweed cut their methane emissions by 60%, increased their hydrogen production by 367% and increased their feed efficiency by up to 74%.

Researchers were also able to reconstruct the genome of Duodenibacillus, a bacterium that has not yet been isolated in a lab. By looking at the bacterium’s complete genetic code, they could understand its role in hydrogen consumption, how it may compete with other hydrogen-utilizing microorganisms, and how it functions in the cow’s rumen more globally. Efforts are now underway to try and isolate this specific Duodenibacillus species for further study.

Other authors of the study include Ermias Kebreab, Pedro Romero and Breanna Roque of UC Davis; Pengfan Zhang of the Innovative Genomics Institute at UC Berkeley; and Nicole Shapiro and Emiley Eloe-Fadrosh of the US Department of Energy Joint Genome Institute. Authors Matthias Hess and Ermias Kebreab are also principal investigators at the IGI. 

This work was supported in part by Lyda Hill Philanthropies, Acton Family Giving, the Valhalla Foundation, Hastings/Quillin Fund, an advised fund of the Silicon Valley Community Foundation, the CH Foundation, Laura and Gary Lauder and Family, the Sea Grape Foundation, the Emerson Collective, Mike Schroepfer and Erin Hoffman Family Fund, an advised fund of Silicon Valley Community Foundation, and the Anne Wojcicki Foundation through The Audacious Project at the Innovative Genomics Institute. The work was also supported by the Shurl and Kay Curci Foundation and by the Office of Science of the US Department of Energy.