Livestock are responsible for around 15% of annual greenhouse gas emissions worldwide. A large part of that is methane, burped from cattle.
These emissions are damaging to the environment, and they’re also problematic for farming efficiency: animals’ digestive systems spend a lot of energy making useless methane. But new research, published in PLOS ONE, has found that a particular genus of seaweed could play a big role in reducing methane made by beef cattle.
- Powdered and fed to cattle, seaweed from the Asparagopsis genus reduced cattle methane burp emissions by more than 80%
- Animals fed the seaweed gained as much weight as herd mates on “regular” diets
- The meat they produced matched the grade and taste of regular-diet product
Lab studies had shown that seaweed in the Asparagopsis genus might be an effective methane antagonist. These seaweeds have gland cells that defend it against chemicals that appear in its natural environment – molecules like bromoform and dibromochloromethane. These molecules are also the precursors to methane in cattle’s digestive systems.
An Australian study had previously identified one species, Asparagopsis taxiformis, as the most promising candidate for removing methane in lab conditions. This new study fed small amounts of the seaweed to cattle to see if these results would play out in real life.
Researchers from CSIRO and James Cook University collected the seaweed, which was freeze-dried in Tasmania and then sent to collaborators in California.
Scientists at the University of California, Davis, ground the seaweed into a powder and added it to the meals of 13 Angus-Hereford beef steers – seven eating 47–56g per day for five months, and six eating 76–99g per day. An additional seven cattle were included as a control group.
Over the next five months, researchers measured the gases produced by the cattle using a commercial tool that measures emissions from individual animals.
They found that steers on the seaweed diet consistently burped less methane than their no-seaweed counterparts. Depending on other variations to their diet – such as foraging and total amount of food eaten – this reduction was as much as 82%.
Encouragingly, steers on the seaweed diet gained as much weight as their herd mates, even when they were consuming less total food. This means the seaweed could be helping the animal to store food more efficiently.
Professional food grading and taste testing on the meat didn’t find a difference between the seaweed-eating cattle and the control group.
The researchers believe this seaweed supplement could make cattle farming more environmentally friendly, as well as improving efficiency for farmers and feeders – and they aren’t the only livestock to love seaweed.
“There is more work to be done, but we are very encouraged by these results,” says Breanna Roque, lead author on the study. “We now have a clear answer to the question of whether seaweed supplements can sustainably reduce livestock methane emissions and its long-term effectiveness.”
“Only a tiny fraction of the earth is fit for crop production,” adds Ermias Kebreab, a professor at UC Davis and co-author on the study. “Much more land is suitable only for grazing, so livestock plays a vital role in feeding the 10 billion people who will soon inhabit the planet. Since much of livestock’s methane emissions come from the animal itself, nutrition plays a big role in finding solutions.
“We now have sound evidence that seaweed in cattle diet is effective at reducing greenhouse gases and that the efficacy does not diminish over time.”
Ellen Phiddian is a science journalist at The Royal Institution of Australia.
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