Reducing Ruminant Methane Emissions
Greenhouse gases such as carbon dioxide and methane are capable of trapping heat within our atmosphere, which, in excess, can cause shifts in global temperatures. Methane gas is approximately twenty-eight times more effective than carbon dioxide in trapping heat; however, methane gas only lives within the atmosphere for approximately twelve years before it is oxidized.
The relatively short lifespan of methane makes it attractive for short-term climate change solutions and can even lead to an atmospheric cooling effect if methane emissions are adequately reduced within the next ten years. Ruminant—think four-chambered stomachs, such as cows and goats—livestock farming contributes approximately thirty percent of total human-induced methane emissions globally; therefore, strategies for reducing ruminant methane emissions can have a considerable impact on climate change.
Ruminant—think four-chambered stomachs, such as cows and goats—livestock farming contributes approximately thirty percent of total human-induced methane emissions globally.
Use of Red Seaweed to Reduce Cow Gas
Our lab at the University of California, Davis, focuses on investigating the effects of feed additives to reduce methane coming from the stomachs of cattle. One feed additive with significant promise of reducing methane is the red seaweed Asparagopsis. The family of Asparagopsis used in the study accumulates halogenated compounds such as bromoform (chloroform with bromine substituting for chlorine) in its plant cells. Bromoform and other haloalkanes are thought to competitively bind to enzymes necessary for reactions within methane formation. Laboratory studies showed that red seaweed almost eliminates methane emissions when added in amounts up to two percent of the total diet. The first-ever study of this type with cattle showed that supplementing diet with about ten ounces of seaweed a day in dairy cows reduced methane emissions by up to sixty-seven percent. However, there was a reduction in dairy feed intake because of the relatively high amount of seaweed offered.
Our lab’s new study was conducted with beef cattle to understand (1) if the microbes responsible for formation of methane in cattle can adapt to the seaweed and, therefore, reduce the seaweed’s effectiveness and (2) if the type of diet changes the effectiveness of the added seaweed in reducing methane emissions.
The beef cattle used in the study were supplemented with 1.5 to three ounces of seaweed per day in their diet for twenty-one weeks. During the initial feeding stages of the project, the cattle were unsure about eating the seaweed in their diet; however, after about two weeks they adapted to this new ingredient. We saw that the microbes did not adapt to the seaweed, and that the seaweed was effective for the entire time the cattle were consuming it. Cattle fed high-forage diets reduced their methane emissions by thirty-three to fifty-two percent, depending on how much seaweed they were given per feeding. Cattle fed low-forage diets had their methane emission reduced by 70 to 80%.
One finding of particular interest for livestock farmers was that cattle supplemented with seaweed were more efficient in converting feed to body weight by up to twenty percent, which reduces the cost of production for farmers. For example, a producer finishing one thousand head of beef cattle has the potential to reduce feed costs by $40,320 to $87,320 depending on how much seaweed was used. The reason for better feed conversion efficiency could be because the resultant increase in hydrogen pressure in the gut pushes the metabolism towards producing a better quality of energy source for the animal.
Feed cost reductions in combination with significantly reduced methane emissions suggest a potential for seaweed supplementation to transform cattle production into a more economically and environmentally sustainable industry.
Supplementing Asparagopsis has produced no measurable bromoform residues nor detrimental iodine residual effects in meat. No difference in meat quality was detected and a consumer panel did not detect any difference in tenderness, juiciness and flavor of meat, whether coming from cows that consumed seaweed or from those that did not. Feed cost reductions in combination with significantly reduced methane emissions suggest a potential for seaweed supplementation to transform cattle production into a more economically and environmentally sustainable industry.
There has also been great interest from seaweed farmers to develop aquaculture techniques globally in ocean and land-based systems to scale up production and meet potential demand. Currently, international research on the ability to scale up Asparagopsis seaweed production is underway. Asparagopsis shows great potential in that it has been found to grow naturally all over the world, including in the waters near Australia, Portugal, Southern California, and Hawaii. The next steps for the use of seaweed as a feed additive would be to obtain approval by the US Food and Drug Administration before it can be used in the commercial cattle industry in the US. Additionally, the development of an emission reduction protocol through the use of seaweed would provide guidance on how to quantify, monitor, and verify methane emission reductions and allow farmers to claim carbon credit from carbon offset programs around the world.
*Ermias Kebreab is Associate Dean and Professor of Animal Science. He holds the Sesnon Endowed Chair and he is the Director of World Food Center, University of California, Davis.
Breanna Roque is a PhD student in the Animal Biology department at University of California, Davis. Her work involves developing strategies to improve environmental sustainability in livestock production through the use of alternative feed additives in ruminant diets.