Innovating the carbon-neutral effort

Feed trial used seaweed to reduce methane in dairy cows


LA CROSSE, Wis. — The effort to reduce methane emissions continues, and feed additives can be a practical approach. Recent research studied the effects of a seaweed product on the reduction of methane emissions in dairy cows.

The study took place under the supervision of Dr. Brad Heins, a professor of organic dairy production at the University of Minnesota. 

The research was conducted at the West Central Research and Outreach Center’s organic farm in Morris, Minnesota. The project was part of Organic Valley’s carbon insetting program. The seaweed product was provided by Symbrosia, of Hawaii.

“Most of the previous studies were done in just a month or two and saw great reductions in methane, so we wanted to find out what happens after six months,” Heins said. “There was one study that found that the rumen microbiome returns to the same as what it did before that, so we wanted to know what happened.”

Heins presented findings at the Marbleseed Organic Farming Conference Feb. 23 in La Crosse.

Methane was measured with a GreenFeed system. The pasture-based system includes a head box that cows enter freely to receive a bait of feed. After two minutes, the box will have measured 3-5 methane emissions. Heins said a cow releases methane about every 45 seconds while eating.

“Contrary to what the world probably thinks, a cow is not releasing methane 24 hours a day,” Heins said. “It is being released in big bursts every minute or so.”

Methane also is released when a cow is digesting feed. Studies have shown that methane emissions are low in the morning and high at night because most dairy farmers put fresh feed down in the morning, and by the end of the day, a cow has a full rumen that is busy digesting feed.

Heins began feeding the seaweed product in July 2023. The product was made from a variety of red seaweed that is high in bromoform, which is a component that reduces methane.

The study included 40 dairy cows that were fed 1 ounce per cow per day. Because this was the company’s first controlled study, they were not sure where to start with intakes. The product was fed in the total mixed ration, and their first discovery was that the cows did not like it. Feed intake was reduced by 60%, even at a rate of 1 ounce per day.

It took two weeks for the cows to adjust to their regular intake. Once their feed intake was adjusted, it took about 3-4 weeks for the rumen microbes to adjust and to see a methane reduction.

At that point, cows were on pasture and  receiving the TMR with the seaweed additive. There was a 30%-40% reduction in methane emissions. This stayed relatively consistent throughout the study until the sixth month when it tapered off. Methane emissions eventually returned to their original levels, while still being fed the seaweed product.

“At that point, their rumen microbes had adjusted back to what they were before we started feeding,” Heins said. “We didn’t see the reduction in methane like we had a few months prior to that.”

Throughout the study, there was no difference in milk production. The cows were in late lactation and producing an average of 30 pounds per day, with tests of about 4.1% fat and 3.1% protein. Somatic cell count, milk urea nitrogen and dry matter intake all stayed relatively unchanged throughout the study.

Cows wore sensors to monitor rumination during the study. Cows fed the seaweed product ruminated about 30 minutes less per day than the control group.

“Maybe the rumen bugs were not as active,” Heins said. “We’re not sure why yet. Was the rumen more efficient at digesting feed? Certainly could be.”

The milk was tested to see if the seaweed product had any adverse effects on the milk and if it was safe for human consumption. They found that milk from a cow that was fed the seaweed product had higher bromide and iodine. They concluded that an adult male or female would have to consume 5 gallons of milk per day to experience adverse effects. A 1-year-old child would have to consume 1 gallon per day to experience negative effects. Because this is possible, consumption is not recommended for small children.

The milk was fed to calves throughout the study, and the calves showed no negative effects.

Rumen samples taken about once a month will be further analyzed by Heins and his students. Heins collected samples from the rumen, fat and liver of culled cows to determine if the seaweed product goes through the digestive system and is accumulated in the liver.

Additionally, milk was saved to be used in a taste-testing study, to see if adults could detect a difference of flavor.

“There needs to be more studies done,” Heins said. “I would love to do another trial, especially at different feeding levels. We did it at a pretty low feeding level, but now, we could do some more with increased feeding levels to see if we could lower the emissions even more. Even at 1 ounce, we got 30%-40% (reduction).”


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