Seaweed cuts methane from cows

cattle feedlot

UNIVERSITY PARK, Pa. — Supplementing cattle feed with seaweed could significantly reduce methane belched by livestock, according to Penn State researchers, but they caution that the practice may not be a realistic strategy to battle climate change.

Asparagopsis taxiformis, a red seaweed that grows in the tropics, decreased methane emission by 80% in short-term studies of lactating dairy cows when fed at up to 0.5% of feed dry matter intake, said Alexander Hristov, distinguished professor of dairy nutrition. The seaweed also had no effect on feed intake or milk yield.

“It looks promising, and we are continuing research” Hristov said.

If a seaweed feed supplement is viable, the scale of production would have to be immense to make a difference globally, Hristov said. With nearly 1.5 billion head of cattle in the world, harvesting enough wild seaweed to add to their feed would be impossible. Even providing it as a supplement to most of the 94 million cattle in the U.S. is unrealistic.

“To be used as a feed additive on a large scale, the seaweed would have to be cultivated in aquaculture operations,” he said. Harvesting wild seaweed would deplete the oceans and cause ecological problems.

Questions raised

Hristov said while it’s effective short term, they don’t know about its long term impact because the microbes in cows’ rumens are highly adaptable. Long-term studies are needed to see if compounds in the seaweed continue to disrupt the microbes’ ability to make methane, he said.

There are also questions about the stability over time of the active ingredients, bromoforms, in the seaweed. These compounds are sensitive to heat and sunlight and may lose their methane-mitigating activity with processing and storage, Hristov said.

Palatability is another question. Cows don’t seem to like the taste of seaweed. When Asparagopsis was included at 0.75% of the diet, researchers observed a drop in the feed intake by the animals.

Also, the long-term effects of seaweed on animal health and reproduction and its effects on milk and meat quality need to be determined. A panel judging milk taste is part of ongoing research, Hristov said.

Cow burps no big deal?

Cows burping — often incorrectly characterized as cows farting — methane and contributing to climate change has been the subject of considerable derision in the U.S., said Hristov, who is recognized as an international leader in conducting research assessing greenhouse gas emissions from animal agriculture.

It is taken seriously in other countries, he said, because the average dairy cow belches 380 pounds of methane a year.

However methane from animal agriculture is 5% of the total greenhouse gases produced in the U.S., Hristov said. Much more comes from the energy and transportation sectors, he said.

“So, I think it’s a fine line with the politics surrounding this subject. Do we want to look at this? I definitely think that we should, and if there is a way that we can reduce emissions without affecting profitability on the farm, we should pursue it.”

Hidden benefits. Hristov said “it is pretty much a given” that if enteric methane emissions are decreased, there likely will be an increase in the efficiency of animal production.

The four tons of seaweed used in the Penn State research was harvested from the Atlantic Ocean in the Azores and shipped frozen from Portugal. After it arrived at the university, it was freeze-dried and ground by the researchers, which was a huge undertaking, Hristov said.

The research project was funded by the U.S. Department of Agriculture’s National Institute of Food and Agriculture and the Jeremy and Hannelore Grantham Environmental Trust.


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