Climate change and ruminants (April 15, 2017)

Animal Science Update

By Michael L. Westendorf, Rutgers University, School of Environmental and Biological Sciences

Food, fiber, and other products form animals contribute significantly to the quality of American life.
Some of these benefits are influences on our diet, upon the wise use of available resources, and the economic vitality of the United States.
In recent years, animal products have been implicated in everything from cardiovascular health to influences on environmental quality.
One recent argument has been that domestic livestock contribute to global warming because of methane emissions.
Particularly, ruminants or cud-chewing animals (cattle, sheep, goats, etc.) have been accused.
There are a number of greenhouse gasses which may contribute to global warming. Among these are carbon dioxide, methane nitrous oxide, and fluorinated gasses. The major greenhouse gas is carbon dioxide contributing more than 60 percent of the total greenhouse gas (CO2 equivalents). Methane contributes about 16 percent of the total (Animal agriculture is responsible for about 33 percent of this), according to Environmental Protection Agency Figures).
Ruminant animals do produce some methane. When a ruminant (cow, sheep, goat, other cud-chewers, etc.) eats a feed that is higher in fiber such as grass, corn silage, or hay, it will be digested by bacterial action in the rumen.
In the process of this digestion, one of the byproducts is methane which will be released into the atmosphere by eructation (belching).
Diets that are higher in grain or other concentrate feeds will lower methane production, but this will be less than the amount produced in diets containing greater amounts of fiber.
The amount of methane produced can be reduced by certain additions to the diets. An ionophore is a feed additive that will increase the efficiency of digestion and the overall feed utilization of the animal.
Bovatec and Rumensin are two commercially available examples. These will reduce the amount of methane produced in the rumen. (These should only be fed to ruminants such as cows or sheep and only according to veterinary and label directions).
Another product that may reach the market is 3-nitrooxypropanol.
This product reduced methane emissions while maintaining milk production in lactating dairy cows.
This research was conducted by Alexander Hristov and co-workers at Pennsylvania State University.
You can find the article at the Proceedings of the National Academy of Science at
In the news recently, you may have seen reports that seaweed in a ruminant diet will reduce methane production and emissions.
Supplementing a species of seaweed, (Asparagopsis taxiformis) into a sheep’s diet reduced methane production by up to 80 percent while live weight gains were maintained. With results this significant, there have been many popular press articles written about the potential that seaweed may have for methane mitigation.
This research was conducted by an Australian research team. It is published in Animal Production Science and can be found at
Non-ruminating species (pigs, horses, poultry, pets, etc.) will also produce some methane by the bacterial activity in their intestines, but this amount is proportionally much less than that produced by ruminants.
On a worldwide basis, livestock animals account for about 33% of total methane production. To put this in perspective it is important to realize that many ruminants other than cattle, sheep, and goats (llama, alpaca, camel, water buffalo, bison, caribou, elk, deer, moose, antelope, etc.) contribute to this total.
The amount of methane produced by domestic ruminants in the United States is a very minor portion of worldwide greenhouse gas production.
In addition, significant amounts of methane are produced by swamps, wetlands, marshes, termites, oceans, forest fires, rice paddies, coal mining and oil and natural gas production, exploration, and extraction.
The greatest greenhouse gas is carbon dioxide that comes primarily from fossil fuels used to power automobiles and industry. Levels of carbon dioxide have increased significantly in the last century.
Even if it were possible to eliminate all methane emissions from animals, the benefits realized might be minor because methane emissions from agricultural animals contribute a relatively small amount of the total — probably about 5 percent of total emissions.
Nevertheless, reducing methane emissions is a reasonable goal.
It is important to recognize again some of the many benefits of livestock animals. In the average American diet, animal products contribute significant amounts of total caloric intake, essential amino acids found in protein, vitamin B-12 and calcium (Dairy products alone provide 75 percent of the calcium in our diets). In addition, many trace and micronutrients such as zinc, manganese, and vitamin B-6 are found in animal products.
The iron found in meat is probably the best and most available form that the human body can use.
Animals and particularly ruminants will continue to play an essential role because of their ability to make use of low quality forages and grazing land that we could not otherwise make use of.