The environmental impact of the beef industry has received increased attention from the public because of perceptions of its effects on climate change. The Intergovernmental Panel on Climate Change estimated that 23 percent of global greenhouse gas emissions were from agriculture, forestry and “other land uses.” Methane is a potent greenhouse gas, and ag, forestry and “other” land uses produce about 44 percent of the methane, with 46 percent of that coming from ruminant animals.
In the U.S., agriculture contributes 9 percent of the total greenhouse gas emissions, with the transportation, industry and electrical sectors producing 79 percent of total greenhouse gases. Of the 9 percent of greenhouse gas emissions attributed to agriculture, 60 percent is attributed to animal agriculture (5.4 percent of total emissions), and within that, 60 percent is methane from all ruminant animal agriculture (3.2 percent of total U.S. emissions).
Life cycle assessments of the U.S. beef industry indicate the cow-calf and stocker segments of the industry produce 70 to 80 percent of the greenhouse gas emissions from the beef sector. This is because cattle consuming a high-forage diet have increased methane emissions, and brood cows live on pastures continuously and have a single offspring per year.
Globally, 75 percent of greenhouse gases from ruminants are produced in developing countries, which produce over two times the amount of greenhouse gases per pound of carcass than in developed countries. This is driven by low feed digestibility, low slaughter weights, higher age at slaughter and poor animal husbandry practices.
Emission rates per pound of product in developed countries (primarily Europe, North America, Australia and New Zealand) are low due to improved grazing management, higher pasture quality and digestibility, and more intensive feeding practices.
Even though livestock’s greenhouse gas emissions are relatively minor in the U.S., methane emissions can be reduced by improving forage quality, such as increasing use of cool-season forages and legumes, and using rotational grazing management.
Reducing methane emissions by acting directly on the grazing animal and not the forage base is problematic, partially due to the difficulty in estimating intake of grazing animals (level of intake is a major driver of enteric methane production), the infrequency of supplementation, and the variable level of individual animal supplement intake.
Common strategies to reduce methane production are supplementation to increase animal performance and providing supplements that directly alter ruminal fiber digestion or methane-producing ruminal bacteria.
Methane mitigation strategies in grazing environments are limited, but producer decisions that improve the nutritional status of animals, a high-quality forage base, and supplementation of methane mitigation compounds can reduce methane production. Thus, management, husbandry and technologies that increase productivity and efficiency of beef production systems can also reduce the environmental footprint of beef. — Paul Beck, Oklahoma State University Extension beef cattle specialist
