Cows produce significant amounts of methane, a potent greenhouse gas, through their digestive process. Each animal emits roughly 200 pounds annually, making livestock a notable contributor to global warming. For decades, reducing methane emissions from cattle without compromising productivity has been a major challenge for scientists and farmers. Recent research offers a breakthrough: red seaweed feed dramatically cuts methane production. However, the underlying microbial mechanisms were not fully understood.
A collaborative study from UC Davis, UC Berkeley, and the Innovative Genomics Institute (IGI) now sheds light on how red seaweed alters the gut microbiome, identifying key microbes that contribute to methane reduction. This knowledge brings researchers closer to engineering gut microbes for long-term, sustainable solutions—moving beyond reliance on seaweed additives.
Seaweed Transforms the Cow Gut
Previous studies demonstrated that red seaweed (genus Asparagopsis ) blocks a crucial enzyme in methane-producing microbes. The new research reveals that seaweed triggers specific gene activations and deactivations in these microbes, indicating their critical role in methane reduction. As these genes switch on and off, hydrogen levels briefly increase within the cow’s gut.
Crucially, the team identified a rumen bacterium, Duodenibacillus, capable of consuming this excess hydrogen. This is significant because high hydrogen levels can cause acidosis in the rumen, harming the animal. Duodenibacillus converts hydrogen into succinate, a compound the cow can use to produce protein.
“That’s important because too much hydrogen can lead to acidosis in the rumen, which can harm the animal,” said Matthias Hess, project leader and UC Davis microbiologist. “Instead, this organism uses the hydrogen and converts it to succinate, a compound the animal can eventually use to make protein.”
Engineering Methane-Reducing Microbes
The findings open the door to engineering microbial communities that outcompete methane producers. By understanding how Duodenibacillus functions, scientists can potentially manipulate the rumen microbiome for greater efficiency.
“Hydrogen is a key energy source in the rumen, specifically for methane-producing microbes,” said Spencer Diamond, principal investigator at 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.”
Experimental Results
Researchers analyzed rumen fluid from eight cows: four on a regular diet and four supplemented with seaweed for 14 days. Cows fed seaweed reduced methane emissions by 60%, increased hydrogen production by 367%, and improved feed efficiency by up to 74%.
The team also reconstructed the genome of Duodenibacillus, a bacterium previously unisolated in the lab. This complete genetic code provides insight into its hydrogen consumption role, competitive dynamics with other microbes, and broader function in the rumen. Efforts are underway to isolate Duodenibacillus for further study.
This research demonstrates that manipulating the gut microbiome is a viable pathway to reduce methane emissions from cattle. By engineering microbial communities that efficiently consume hydrogen, scientists can create more sustainable and climate-friendly livestock systems
