Seaweed Reduces Methane Emissions in Grazing Cattle by 40%

Researchers have discovered that a seaweed-based supplement significantly reduces methane emissions from grazing beef cattle by nearly 40% without impacting their health or weight, offering a sustainable solution to one of the major contributors to global greenhouse gases.

Seaweed is proving to be a promising tool for making cattle farming more sustainable. Researchers at the University of California, Davis, have discovered that feeding grazing beef cattle a pelletized seaweed supplement can reduce their methane emissions by nearly 40%, with no negative effects on their health or weight. These findings were published today (December 2) in the Proceedings of the National Academy of Sciences.

This groundbreaking study is the first to examine the effects of seaweed on grazing beef cattle, building on earlier research that demonstrated seaweed could cut methane emissions by 82% in feedlot cattle and more than 50% in dairy cows.

Methane Emissions From Cattle: A Global Issue

Livestock account for 14.5% of global greenhouse gas emissions, with the largest portion coming from methane that cattle release when they burp. Grazing cattle also produce more methane than feedlot cattle or dairy cows because they eat more fiber from grass. In the U.S., there are 9 million dairy cows and over 64 million beef cattle.

“Beef cattle spend only about three months in feedlots and spend most of their lives grazing on pasture and producing methane,” said senior author Ermias Kebreab, professor in the Department of Animal Science. “We need to make this seaweed additive or any feed additive more accessible to grazing cattle to make cattle farming more sustainable while meeting the global demand for meat.”

Innovative Solutions for Pastoral Farming

Kebreab said that daily feeding of pasture-based cattle is more difficult than feedlot or dairy cows because they often graze far from ranches for long periods. However, during the winter or when grass is scarce, ranchers often supplement their diet.

For this study, researchers divided 24 beef steers (a mix of Angus and Wagyu breeds) into two groups: one received the seaweed supplement, and the other did not. Researchers conducted the 10-week experiment at a ranch in Dillon, Montana. Since these were grazing cattle, they ate the supplement voluntarily, which still resulted in a nearly 40% cut in emissions.

Most research to reduce methane emissions using feed additives have taken place in controlled environments with daily supplements. But Kebreab noted in the study that fewer than half of those methods are effective for grazing cattle.

Potential Impact on Global Farming Practices

“This method paves the way to make a seaweed supplement easily available to grazing animals,” said Kebreab. “Ranchers could even introduce the seaweed through a lick block for their cattle.”

Kebreab said pastoral farming, which includes large grazing systems, supports millions of people around the world, often in areas vulnerable to climate change. This study suggests a way to make cattle grazing better for the environment and play a role in fighting climate change.

Supporting Global Meat Demand Sustainably

A related article in the same PNAS issue highlights the need to improve the efficiency of livestock production in low- and middle-income countries using better genetics, feeding, and health practices. UC Davis Professor and Cooperative Extension Specialist Alison Van Eenennaam, the article’s author, said it is the most promising approach to meet the global demand for meat while limiting greenhouse gas emissions.

Reference: “Mitigating methane emissions in grazing beef cattle with a seaweed-based feed additive: Implications for climate-smart agriculture” by Paulo Meo-Filho, John F. Ramirez-Agudelo and Ermias Kebreab, 2 December 2024, Proceedings of the National Academy of Sciences.
DOI: 10.1073/pnas.2410863121

Other authors of the seaweed study include UC Davis postdoctoral researchers Paulo de Méo Filho Paulo Meo-Filho and John-Fredy Ramirez-Agudelo.

The research was supported by Matador Ranch in Dillon, Montana.

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