Beef steers graze on a ranch in Dillon, Montana. The machine nearby releases a seaweed supplement while also measuring the cattle's methane emissions. (Paulo de Méo Filho / UC Davis)
Beef steers graze on a ranch in Dillon, Montana. The machine nearby releases a seaweed supplement while also measuring the cattle's methane emissions. (Paulo de Méo Filho / UC Davis)

Feeding Grazing Cattle Seaweed Cuts Methane Emissions by Almost 40%

Findings Offer Solution for More Climate-Friendly Cattle Farming

Quick Summary

  • First-Ever Study To Test Seaweed on Grazing Cattle
  • Reducing Methane Emissions in Grazing Cattle More Difficult Than Feedlot or Dairy Cows
  • Nearly 40% Reduction in Methane Emissions Plays Role in Fighting Climate Change

Seaweed is once again showing promise for making cattle farming more sustainable. A new study by researchers at the University of California, Davis, found that feeding grazing beef cattle a seaweed supplement in pellet form reduced their methane emissions by almost 40% without affecting their health or weight. The study was published today (Dec. 2) in Proceedings of the National Academy of Sciences.

This is the first study to test seaweed on grazing beef cattle in the world. It follows previous studies that showed seaweed cut methane emissions 82% in feedlot cattle and over 50% in dairy cows.

How much methane do cattle produce?

Overhead view of the machines that dispense the seaweed supplement and measure the grazing cattle's methane emissions. The solar panels power the machines. (Paulo de Méo Filho / UC Davis)
Overhead view of the machines that dispense the seaweed supplement and measure the grazing cattle's methane emissions. The solar panels power the machines. (Paulo de Méo Filho / UC Davis)

Livestock account for 12% 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.”

 

Difficulty in lowering grazing cattle emissions

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. 

Beef steer graze on a ranch in Montana. (Paulo de Méo Filho / UC Davis)
Beef steer graze on a ranch in Montana. (Paulo de Méo Filho / UC Davis)

 

Most research studies 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.

“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, while playing a role in fighting climate change.

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.

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

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

Media Resources

  • Ermias Kebreab, Department of Animal Science, ekebreab@ucdavis.edu, (Ermias Kebreab is in Vietnam, GMT+7, from Dec. 2-9, but available via email to schedule a time for an interview)
  • Amy Quinton, News and Media Relations, amquinton@ucdavis.edu, (530) 601-8077

    Full research paper and photos for download, with credit.

    For more information on emissions in livestock, see the most recent report from the Food and Agriculture Organization of the United Nations.

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