When it comes to protecting the environment, don't blame greenhouse gas emission problems on beef cattle or people who like a good steak.
Not only is bovine flatulence not to blame, 98 percent of methane emissions from cattle are released through their mouth in a process called eructation, according to researchers at Oklahoma State University and reported by Drovers Cattle Network.
"As with the production of all foods, beef production results in greenhouse gas emissions; however, the U.S. Environmental Protection Agency estimates direct emissions from the U.S. beef industry are only 1.9 percent of the total U.S. greenhouse gas emissions," said Sara Place, assistant professor of sustainable beef cattle systems for OSU. By comparison, transportation and electricity accounted for 25.8 percent and 30.6 percent of total U.S. greenhouse gas emissions in 2013.
Even without consideration of any unintended consequences and impacts of alternative protein sources, completely removing beef from the U.S. diet would likely not result in huge declines in greenhouse gas emissions, but could have negative implications on the sustainability of the nation's food system.
"Cattle have the ability to utilize grass forages and byproducts such as distiller's grains that are not fit for human consumption," Place said. "Specifically, cattle can utilize cellulose, one of the world's most abundant carbon-containing molecules that are inedible to humans. Consequently, U.S. beef producers feed their cattle from food sources that are not in direct competition with human nutritional resources."
In addition, cattle can convert low-quality feeds grown on lands not suitable for cultivation that humans won't eat into high-quality protein that can sustain humans, thereby reducing soil erosion and enhancing carbons storage, both of which provide significant environmental benefits.
And integrated crop and beef systems -- using cattle to graze crop residues and cover crops -- can lead to positive, sustainable environmental outcomes. "Environmental stewardship is as key an aspect as animal well-being and operational economics when we talk about sustainability in beef cattle systems," Place said.
Wheat bran for pigs
Research by the University of Illinois is helping determine the nutritional value of wheat bran in diets fed to pigs.
Wheat bran, like many other co-products from the human food industries, contains more fiber than corn and soybean meal, which adversely affects energy digestibility.
"To save on feed costs, more producers are turning to co-products," U of I professor of animal sciences Hans Stein said. "Therefore, there is a need to determine the energy contribution from fiber-rich ingredients."
In collaboration with colleagues at China Agricultural University in Beijing, growing barrows were fed diets containing 0, 15 or 30 percent wheat bran. The digestible energy, metabolizable energy and net energy in the diets declined as more wheat bran was included.
The DE content of diets containing no wheat bran was 3,454 kcal/kg, compared with 3,161 kcal/kg in diets containing 30 percent wheat bran. The ME content of the diets decreased from 3,400 to 3,091 kcal/kg, and NE content decreased from 1,808 to 1,458 kcal/kg.
The research also validated a procedure commonly used to determine NE. Using the difference procedure, Stein's team determined the DE, ME and NE of wheat bran to be 2,168, 2,117 and 896 kcal/kg, respectively. These values were similar to those derived through regression.
"Because experiments to determine NE via the difference procedure are more difficult to conduct than determining DE and ME, it's helpful to know that using regression to determine NE will yield an accurate value," Stein said.