The EPA reported that agriculture contributed 10% of the greenhouse emissions in 2019. One-quarter of this 10% was methane, which is primarily generated by ruminant animals as part of their normal digestive processes. In total, beef cattle only account for 2% of greenhouse gas emissions.

“Cattle and other ruminants have a specialized digestion system which allows them to digest and metabolize vegetation that is undigestible by non-ruminants. Cattle break food into pieces by chewing as they eat,” explains Joe Paschal, Ph.D., Texas A&M AgriLife Extension. “As a cow chews, digestive enzymes in saliva are mixed with the food before it passes down the esophagus into the reticulum and rumen. Some of the larger food particles are regurgitated, chewed again and re-swallowed. This second chewing is referred to as chewing the cud.”

Food is fermented and further broken down in the rumen by microbes. Carbohydrates in the diet degrade to volatile fatty acids (VFA) and carbon. The VFA are absorbed directly from the rumen, and the carbon reacts with oxygen and hydrogen to form carbon dioxide and methane, respectively. Methane and carbon dioxide are expelled by the ruminant primarily through belching. Although cattle are responsible for only a small percentage of methane and carbon dioxide emissions into the atmosphere, ongoing research is revealing ways to reduce these small amounts even further while improving cow productivity.


New nutrition technology in the feed industry is researching ways for those forages, grains or supplements eaten by cattle to create less of an emission effect on the environment.

Locus Animal Nutrition, a new operating division of Locus Fermentation Solutions, is one company developing a direct-fed microbial feed additive, or probiotic, to potentially reduce methane production by as much as 78% in in vitro studies. The company claims the non-GMO organism improves ruminant digestion, which results in reduced methane production along with improved growth and productivity.


By definition, a probiotic is a micro-organism introduced into an animal’s body for its beneficial qualities. Current primary objectives of using probiotics in animal feed or water is to maintain and improve growth and production as well as to control intestinal pathogens. For instance, probiotics are showing great promise as alternatives to antibiotic growth promoters and in prevention of calf scours.

Locust Animal Nutrition plans on marketing their new product within the next 12 months with strategic distribution partners. Currently, researchers at University of California, Davis are completing additional studies on the probiotic.


Researchers at UC Davis have also reduced methane emissions by adding a seaweed, Asparagopsis taxiformis, to a cow’s diet. They learned that small amounts of the seaweed inhibit activity of a digestive enzyme known to produce methane.

“In a recent beef animal study, methane emissions were reduced by 82 percent when fed about three ounces of A. taxiformis per day,” says Breanna Roque, Ph.D. graduate student. “Twenty-one steers housed in a feedlot were fed the seaweed over a 21-week experimental period. Cattle fed A. taxiformis ate smaller amounts of their diet and gained as much weight as their untreated herdmates, which indicates the additive may increase feed efficiency. A taste-test panel found no differences in taste, tenderness, juiciness and overall flavor of the meat.”

“Scientists are studying ways to raise A. taxiformis, since there is not enough of it in the seas for broad application in cattle feed. Another challenge is to develop a way to feed seaweed to grazing cattle that are not given supplemental feed on a regular basis. That is the subject for my next study,” says Dr. Ermias Kebreab, professor and Sesnon Endowed Chair of the University of California Department of Animal Science.

Diet alterations

Where it is practical, cattle diet alterations can reduce methane emissions and may increase profit. Methane is produced in the cow’s rumen by microbes, and some species produce more than others. Microbes involved in digesting cellulose-rich diets of grass or hay are different than those that digest carbohydrate-rich diets of corn or distillers grains.

Less methane is produced from carbohydrate-rich diets due to propionate production. Propionate or propionic acid is a three-carbon VFA produced by starch and sugar digestion bacteria. As an unsaturated fat, propionate uses hydrogen to become saturated, which makes H2 unavailable for methane production. Methane emitted by the animal is also reduced by grinding and pelleting forage, which increases digestion rate.

Agriculture and Agri-Food Canada (AAFC) scientists at the Lethbridge Research Centre in Alberta have found that adding dietary fat to the ration can reduce methane emissions by as much as 20%. Sources of dietary fat include sunflower seed, canola seed, flaxseed, dried corn distillers grain, whole cottonseed, plant oils and some ethanol byproducts. Fat reduces methane production because it is often toxic to methane-producing microbes. In the AAFC studies, methane was reduced by 5% for each percent of crude fat added to the diet.

“Adding more grain to the ration also reduced methane emissions, but this practice has some limitations since a cow’s digestion system is designed to utilize fibrous feeds. We learned that corn grain produces less methane than barley grain during ruminant digestion,” says Dr. Karen Beauchemin, a livestock specialist with AAFC. “Feeding high-quality forages such as corn silage and alfalfa is another way to reduce methane emissions. The team is currently evaluating feed additives including plant extracts such as condensed tannins, saponins and essential oils as well as rumen modifiers such as yeast, microbials and enzymes.”


“An ionophore is a chemical feed additive that promotes microbe populations that create propionate rather than acetate fatty acids,” says Paschal. “Propionate is the most absorbable and less likely to create methane than acetate fatty acids. Almost all feedyards add ionophores to their feed rations because they increase feed efficiency and weight gain in addition to reducing methane emissions. The United States is the only country that widely uses these feed additives.”

Changes in cattle diets and feed processing may offer feasible options for reducing methane emissions in stocker and feedlot operations; however, opportunities to employ these methods in cow-calf range programs are probably limited. It appears that the probiotic product in development by Locus Animal Nutrition will offer an opportunity for cow-calf producers to further reduce methane emissions while improving productivity. end mark

PHOTO: Methane and carbon dioxide are expelled by the ruminant primarily through belching, although cattle are responsible for only a small percentage of methane and carbon dioxide emissions. Photo by Robert Fears.

Robert Fears is a freelance writer based in Georgetown, Texas.