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Seaweed for Cattle Feed

Written by Dr. Tomotaroh Granzier-Nakajima
Published on December 1, 2022
Research Highlights

Methane is a large source of greenhouse gas emissions in the United States.

Beef and dairy cattle produce over a quarter of the United States’ methane emissions.

Seaweed can reduce methane emissions when introduced as an additive in cattle diets.

Current global seaweed production is not sufficient for mass adoption in U.S. cattle diets.

Beef and dairy cattle produce over a quarter of the United States’ methane emissions.

Greenhouse gases trap heat in the atmosphere. Methane accounts for 11% of U.S. greenhouse gas emissions and are emitted from livestock for agriculture, the production and distribution of natural gas and crude oil, and coal mining (EPA 1, 2022). Around 58% of global methane emissions come from humans (EPA 1, 2022).

The agriculture sector is the largest source of methane emissions in the United States (EPA 1, 2022). When livestock such as cows, pigs, and sheep digest food, they produce and emit methane. This process is estimated to produce around 27% of the United States' methane emissions (EPA 1, 2022).

  • 72% of livestock methane emissions come from beef cattle (EPA 2, 2022).
  • 25% of livestock methane emissions come from dairy cattle.
  • 3% of livestock methane emissions come from other livestock including horses, sheep, pigs, and American bison.

Seaweed additives in cattle diets can reduce methane emissions.

Preliminary experiments have introduced seaweed for up to 1% of dairy and beef cattle diets. In these tests, different types of red seaweed resulted in the largest methane emissions reductions. This may be due a compound in the seaweed called bromoform that reduces gut microorganisms that emit methane (Vijn, 2020).

  • Seaweed in dairy and beef cattle diets can reduce digestion-related methane emissions by up to 67% and 98% respectively (Kinley, 2020; Roque, 2019).

The difference in the reduction in methane emissions between beef and dairy cattle could be due to the different types of seaweed used or the different breeds of cattle used.

Seaweed may improve the growth and dairy production of cattle.

Beef and dairy cattle fed with seaweed required less feed in order to gain weight (Lean, 2021). In some cases, dairy cows fed diets with seaweed produce more milk than cows without seaweed (Roque, 2019; Sefenoni, 2021).

Seaweed contains elements like bromoform and iodine that can get into animal products when used as feed.

Bromoform is suspected to cause cancer, and the Environmental Protection Agency (EPA) has set a limit of 0.08 mg/L for bromoform in drinking water (EPA, 2018; EPA, n.d.).

  • Bromoform has been found at hundreds of times below the EPA limit in milk from cows fed seaweed and it has not been found in beef (Kinley, 2020; Roque, 2021).

Beef and milk from cows fed seaweed have elevated levels of iodine (Stefenoni, 2021). While beneficial for those with insufficient iodine, excess iodine intake can lead to thyroid problems (Vijn, 2020; IM, 2001). The National Academies of Science has defined upper limits for safe iodine consumption based on age and other factors such as pregnancy (IM, 2001).

  • The iodine levels in beef were found to be well below these upper limits (Roque, 2021).
  • One study found that the iodine levels in milk were elevated high enough to surpass the upper limit if enough milk is consumed, particularly for young children (Stefenoni, 2021). However, these results need to be replicated before conclusions are drawn.

There are multiple barriers to adopting seaweed into cattle feed diets at a large scale.

In 2018, 32 million tonnes of seaweed was produced globally, tripling since 2000 (Figure 1) (FAO, 2020). Over 95% of the production is in China, Indonesia, South Korea, and the Philippines (FAO, 2020).

  • Including seaweed as 1% of the diet for all U.S. cattle requires about 3.2 million metric tons of dry seaweed per year (Vijn, 2020). This represents over half of the current global production.

Incorporating seaweed into cattle diets may increase costs for livestock farmers.

Financial incentives may be necessary for seaweed adoption if increased beef or milk yields do not outweigh feed costs (Vijn, 2020). Improved feed efficiency could decrease the amount of feed necessary to raise cattle and reduce feed costs, which often comprise a large portion of costs on a farm (Roque, 2021). However, currently there are no scientific studies that have comprehensively investigated the economic costs for farmers to implement seaweed in cattle feed.

The U.S. Food and Drug Administration (FDA) recognizes a few seaweed species as generally safe (FDA, 2022).

These seaweeds are not required to undergo premarket review and approval by the FDA. More research may be needed to classify the types of seaweed that reduce methane emissions as generally safe according to FDA regulations (Vjin, 2020).

  • In March 2022, the California Department of Food and Agriculture approved one of the most effective red seaweeds for cattle as a digestive aide, on the basis that no negative effect was observed on animal health or milk production (CFRP, 2022).



California Department of Food and Agriculture Commercial Feed Regulatory Program (CFRP). (2022). (rep.). Quarterly Feed Update. Retrieved November 30, 2022, from https://www.cdfa.ca.gov/is/ffldrs/pdfs/QuarterlyFeedUpdate_2022_Q3.pdf 

Institute of Medicine (IM). (2001). Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc. Washington, DC: The National Academies Press. https://doi.org/10.17226/10026. 

FAO. (2020). (rep.). The State of World Fisheries and Aquaculture. Food and Agriculture Organization of the United Nations. Retrieved November 30, 2022, from https://doi.org/10.4060/ca9229en 

Kinley, R. D., Martinez-Fernandez, G., Matthews, M. K., de Nys, R., Magnusson, M., & Tomkins, N. W. (2020). Mitigating the carbon footprint and improving productivity of ruminant livestock agriculture using a red seaweed. Journal of Cleaner Production, 259, 120836. https://doi.org/10.1016/j.jclepro.2020.120836  

Lean, I. J., Golder, H. M., Grant, T. M., & Moate, P. J. (2021). A meta-analysis of effects of dietary seaweed on beef and dairy cattle performance and methane yield. PLOS ONE, 16(7). https://doi.org/10.1371/journal.pone.0249053  

Roque, B. M., Salwen, J. K., Kinley, R., & Kebreab, E. (2019). Inclusion of Asparagopsis Armata in lactating dairy cows’ diet reduces enteric methane emission by over 50 percent. Journal of Cleaner Production, 234, 132–138. https://doi.org/10.1016/j.jclepro.2019.06.193  

Roque, B. M., Venegas, M., Kinley, R. D., de Nys, R., Duarte, T. L., Yang, X., & Kebreab, E. (2021). Red Seaweed (asparagopsis taxiformis) supplementation reduces enteric methane by over 80 percent in Beef Steers. PLOS ONE, 16(3). https://doi.org/10.1371/journal.pone.0247820  

Stefenoni, H. A., Räisänen, S. E., Cueva, S. F., Wasson, D. E., Lage, C. F. A., Melgar, A., Fetter, M. E., Smith, P., Hennessy, M., Vecchiarelli, B., Bender, J., Pitta, D., Cantrell, C. L., Yarish, C., & Hristov, A. N. (2021). Effects of the Macroalga asparagopsis taxiformis and oregano leaves on methane emission, rumen fermentation, and lactational performance of Dairy Cows. Journal of Dairy Science, 104(4), 4157–4173. https://doi.org/10.3168/jds.2020-19686  

U.S. Environmental Protection Agency (EPA). (n.d.). Bromoform. EPA. Retrieved November 30, 2022, from https://iris.epa.gov/ChemicalLanding/&substance_nmbr=214  

U.S. Environmental Protection Agency (EPA). (2018). (rep.). 2018 Edition of the Drinking Water Standards and Health Advisories Tables. Retrieved November 30, 2022, from https://19january2021snapshot.epa.gov/sdwa/2018-drinking-water-standards-and-advisory-tables_.html. 

U.S. Environmental Protection Agency (EPA 1). (2022, May 16). Overview of Greenhouse Gases. EPA. Retrieved November 30, 2022, from https://www.epa.gov/ghgemissions/overview-greenhouse-gases 

U.S. Environmental Protection Agency (EPA 2). (2022, April 14) Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2020. U.S. Environmental Protection Agency, EPA 430-R-22-003. https://www.epa.gov/ghgemissions/inventory-us-greenhouse-gas-emissions-and-sinks-1990-2020. 

U.S. Food & Drug Administration (FDA). (2022, July 20). CFR - Code of Federal Regulations Title 21. FDA. Retrieved November 30, 2022, from https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/CFRSearch.cfm?fr=582.30  

Vijn, S., Compart, D. P., Dutta, N., Foukis, A., Hess, M., Hristov, A. N., Kalscheur, K. F., Kebreab, E., Nuzhdin, S. V., Price, N. N., Sun, Y., Tricarico, J. M., Turzillo, A., Weisbjerg, M. R., Yarish, C., & Kurt, T. D. (2020). Key considerations for the use of seaweed to reduce enteric methane emissions from cattle. Frontiers in Veterinary Science, 7. https://doi.org/10.3389/fvets.2020.597430  

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