A new study by the University of California, Davis, discovered that feeding a seaweed supplement in pellet format, to grazing beef cattle, has been proven to reduce methane emissions by almost 40%, without negligible impacts to the animal’s health or weight.
The test was published in the journal ‘Proceedings of the Academy of Sciences’ on Monday, December 2, following previous studies conducted in dairy cows in 2019 and feedlot cattle in May 2024.
Speaking about the potential impact of the study, senior author and professor at the Department of Animal Science, Ermias Kebreab, said:
“Beef cattle spend only about three months in feedlots and spend most of their lives grazing on pasture and producing methane.
“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.”
The study was conducted over the course of 10 weeks on a ranch in Dillon, Montana, where scientists divided 24 beef steers, crossbreeds of Angus and Wagyu, into two distinct groups, one of which was fed with the seaweed supplement, the other, the control group, was not.
Seaweed supplement
Researchers trialed and assessed three phases of supplement intake: a three week ramp-up phase, a three week optimal phase, and a two week decreasing phase.
The animals in question underwent routine weigh-ins every 14 days and methane emissions were monitored on a regular bases using a Greenfeed system, which can be described as a feed lot on a trailer with technology to measure gas influxes from individual animals.
No differences were observed between the two groups throughout the study, which included the weekly, initial and final liveweight, average daily weight gain and predicted dry matter (DM) intake.
However, methane emissions were down an average 37.7% in the herd that were fed the seaweed supplement, in comparison to the control group, which indicates that seaweed containing feed additives are effective at combating methane emissions in grazing cattle.
While the control group continued to emit stable levels of methane throughout the 10 weeks, the second group exhibited a notable reduction in methane emissions after day 16 of introducing the supplement into their diet.
This reduction persisted throughout the subsequent five-week period which included the optimal and decreasing phases, consistently remaining below the control group’s emissions.
In the U.S., there are nine million dairy cows and over 64 million beef cattle, researchers have claimed.
Methane emissions from livestock are accountable for 16 – 17% of global greenhouse gases and grazing cattle have been shown to produce more methane emissions than feedlot cattle due to the higher propensity of fiber in their diets, according to the study’s authors.
Unlike carbon dioxide, which can remain in the atmosphere for centuries, methane only has a lifespan of about 12 years.
However, what it lacks in longevity, it compensates for in potency, as methane is considered 80 times more effective at absorbing heat than carbon dioxide, which increases its contribution to global warming.
Previous studies conducted in the area had discovered a drop in dry matter intake (DMI) within the bovines supplemented with seaweed that did not occur in this study, which researchers believe, was due to a lower concentration of seaweed in the diet.
The observed 37.7% average reduction in methane production, achieved without an adverse affect on bovine performance, indicates a promising approach for mitigating the environmental impact of livestock farming.
“This method paves the way to make a seaweed supplement easily available to grazing animals, ranchers could even introduce the seaweed through a lick block for their cattle,” Prof. Kebreab said.
