Seaweed in the Feed Bunk: Does It Cut Methane and Does It Pay?

Every few months somebody sends a story about feeding seaweed to cows to cut methane. Fine. But a cattleman wants to know three things: does it work, can I feed it, and who is paying for it? The research is further along than the skeptics say and less settled than the promoters say. Here is what the trials actually found.

The short version of the science

Cows make methane when microbes in the rumen break down feed. A compound in red seaweed called bromoform, found in the species Asparagopsis, blocks the last step in that process. Feed enough of it and methane drops. How much drops depends on dose, diet and how well the animal eats it.

What the trials found

A University of California, Davis trial published in a leading journal put a pelleted seaweed product in front of 24 Wagyu-Angus steers for 70 days on irrigated pasture. Enteric methane fell an average of 37.7 percent in the main phases, and gain did not differ between treated and control steers, according to the paper on PubMed Central. Pasture made up more than 95 percent of what the steers ate, so it looks a lot like real grazing.

The authors admitted the limits. Small herd, short trial, and the steers ate less of the additive late in the study, probably over taste. The effect dropped with the intake. Hydrogen went up, and the lead author had a tie to the company that supplied the product.

An earlier UC Davis feeding trial with 21 Angus-Hereford steers reported cuts of up to 80 percent at the high dose on a low-forage ration, and about 45 and 68 percent overall at the low and high doses, according to Beef Central. That article noted the study was small and partly supported by a company that sells the product.

In Australia, the University of Adelaide put an Asparagopsis extract oil into the diet of 80 Angus cows on extensive grazing for eight weeks and reported methane cuts from 49 to 77 percent, per its own release. It said dosage still needs work.

Notice the pattern. Everyone sees a cut, and the size of the cut moves a lot with the diet and the dose. Do not let a salesman quote you one number.

The practical problem: getting it in the cow

On a feedlot, dosing is simple, because the bunk carries it. On a big pasture, you have to get each cow to eat a steady amount. That means a supplement station or a hand-fed pellet, and anyone who has tried to get cows on range to eat a measured amount of anything knows the trouble. The Montana trial used units that recognized each steer by his ear tag. Most ranches do not have that gear.

Run it like any other input

Treat it like a mineral or a feed additive and ask the usual questions.

• Cost per head per day. Get a delivered price in writing.
• What do I get back? Today most producers get no direct payment for lower methane. Unless a buyer or program pays for it, it is a cost.
• Does it hold up in storage? The active compound can vary between products and fade over time. Ask for a test.
• Is it cleared for use? Rules on feeding it, and on residues in meat and milk, are still developing. Ask your vet and your buyer before you start.
• Does it fit my system? If your cattle graze all year with no feeding station, delivery is the problem to solve first.

Safety and handling

Any new additive should go through your vet before it goes through your cattle. Ask about the form of the product, the feeding rate that was used in the studies, any withdrawal or residue questions, and whether it is cleared for use where you live. Keep the product dry and out of the sun, follow the label, and write down what you fed and when. Records on dose and intake are the only way you will ever know whether it did anything on your place, and they will matter if a buyer asks.

What to do while it sorts itself out

Do not rush. The same dollars spent on fertility, culling open cows, better forage and growth genetics reduce the methane you produce per pound of beef, and they pay you back in calves and pounds. See our piece on climate targets for how those pieces fit together, and our cost per cow breakdown for finding the dollars. If a buyer ever does offer a premium for documented reductions, you will be ready with records.

For more on how feed is formulated and what each ingredient does, read farm.fm's page on feeding programs for Angus herds. To find a nutritionist or extension office near you, check agriculture.directory.

Research and regulations change, so read the original studies and confirm current rules before you buy. This site is independent and not affiliated with the American Angus Association or Certified Angus Beef.