In the face of environmental concerns about methane production from agriculture, dairy producers are reminded that optimum production actually leads to a more environmentally friendly approach to milk production.

That’s according to South Dakota Cooperative Extension Dairy Specialist Alvaro Garcia, who said that methane from agriculture results primarily from fermentation in the gastrointestinal tracts of ruminants due to their particular digestive system.

“According to the Intergovernmental Panel on Climate Change report from 2001, agriculture is responsible for nearly half of the overall methane emissions attributed to human activities,” Garcia said.

Garcia said that the people who question the dairy industry’s use of fed grain often ask why grain and its byproducts are used at all, when those feedstuffs could be used for human consumption.

“While it is true that the more feed cows eat, the more methane they produce, when they are fed grain, cows capture hydrogen more efficiently,” said Garcia. “Their metabolism captures hydrogen, and less methane is produced. At the same time, cows with good genetic potential that are eating more grain sustain higher milk production.”

Even in the face of questions about raising milk production higher when a lot of milk is in the market, Garcia said it still makes sense environmentally.

“With greater productivity, less cows are needed to reach a given total milk output and less methane is produced per pound of milk, with less methane overall load to the environment,” Garcia said. “Truly, the ‘environmentally friendly’ approach is to feed cows to their genetic potential for milk production and to have the land base where the nutrients excreted in the manure as a natural fertilizer can be applied.”

In regions or states with intrinsic dairy production advantages, producers need to make the most of those advantages and optimize the number of cows for a given milk production market.

Garcia said that while the dairy industries of individual states are currently ranked by the number of cows and total milk produced, it would make sense to change the ranking to fit concerns about the environmental impact of methane.

“It would be reasonable to rank states based both on their milk production and their methane contributions to the environment,” Garcia said. “Research reported in 2007 by Ellis and coworkers from the Canadian University of Guelph provides a reliable estimate of daily methane production per cow from daily dry matter intake, so we have the data we need to give the public a more fully formed image of the industry state-by-state.”

Methane emissions often are measured in megajoules (MJ) and terajoules (TJ). One million joules make one MJ, while one million MJ make one TJ.

“In simple terms the more cows eat, the more methane they produce, and the overall methane output per state can be estimated by using the expected dry matter intake and the total number of cows,” Garcia said. “Using this formula, states that have the most cows will obviously rank first in total methane production.”

In 2008, the leading states in cow numbers were California, with 1.84 million dairy cows and Wisconsin, which has 1.25 million. During the same year, South Dakota was ranked 25th.

“Similarly, in 2008, California produced 32 TJs of methane per day from dairy cows, which was nearly 20 percent of the U.S. total, and Wisconsin was second with almost 22 TJ,” said Garcia. “South Dakota was a distant 25th with 1.6 TJ.”

Garcia said that while estimates of the total methane output for each state would show the major methane emitters are states with more cows, the dairy efficiency must be considered. The efficiency of methane emissions as it relates to milk produced by each state is the important number, Garcia said.

“If we were to look at that ranking, a state needs to have as low as possible a score in terms of methane produced per pound of milk produced,” Garcia said. “South Dakota ranks 39th with 0.27 MJ of methane produced per pound of milk.”

In 2007, at meetings of the National American Dairy Science Association, Garcia and Linn reported an average output of 0.33 MJ of methane per pound of milk in the U.S.

“States with less methane emissions than South Dakota on a per pound of milk basis were Iowa, Texas, Kansas, Nevada, Utah, Michigan, California, Idaho, Colorado, New Mexico, Washington, and Arizona,” Garcia said. “These are the very states that are above South Dakota in yearly production per cow, which underscores the importance of increasing production per cow. With efficiency comes a reduction in methane emission per pound of milk produced, so it does make environmental sense.”