By Russ Quinn
DTN Staff Reporter
OMAHA (DTN) -- Recent studies conducted on energy supplementation of grazing beef cattle offer the potential to decrease greenhouse gas (GHG) emissions, specifically methane. Common practices of cattle producers can decrease the carbon footprint of beef production, but additional research will be needed to examine different ways to improve the response, according to one scientist studying the issue.
In a Great Plains Grazing webinar on Tuesday afternoon, "Great Plains Grazing," Andy Cole, research animal scientist at USDA-Agricultural Research Service Conservation and Production Research Laboratory in Bushland, Texas, reported on studies being conducted at his facility which examine the effects on the carbon footprint of grazing cattle using different feed supplementation strategies. While the results varied some from study to study, generally the research showed GHG levels could be lowered in grazing livestock.
MORE GHG FROM GRAZING?
Cole said past GHG studies on North American beef cattle production have shown about 87% of the carbon dioxide equivalent is produced while cattle are grazing. Specifically 70% is from cow/calf production, around 17% from stocker operations and just 13% is from the feedlot side, a fact that might surprise.
"This is a lot different than what most people believe," Cole said.
About 60% of GHG from beef production in North America is from enteric methane from the rumen and the lower gut, he said. Roughly 20% comes from manure and another 19% is from energy and secondary emissions.
Cole points out that enteric methane production of U.S. feedlot cattle may already be close to biologically minimized, stating it runs 2% to 4% of the gross energy intake of the animals. If you get much lower than this level, you run into problems with fermentation within the rumen of the animal, he said.
"The greatest opportunity to decrease the carbon footprint appears to be in grazing cattle," he said. "Therefore in the last several years we have conducted a series of studies to examine the effects of supplementation on the emissions from cattle grazing in different forage systems."
Because of seasonal changes in crude protein levels in native rangeland, cattlemen often have to supplement to meet their grazing cattle's nutritional needs. For a mid-sized spring calving beef cow, the amount of crude protein needs to be supplemented during the time from late fall to spring when grass begins to grow.
The effects of GHG emissions from supplements in beef cattle are not fully known, he said.
In one USDA-ARS study, cross-bred steers were fed low quality bluestem hay and then were fed cottonseed meal or dried distillers grain. Methane and carbon dioxide emissions were then measured, Cole said.
Protein supplementation increased total enteric methane and metabolic carbon dioxide due to increased feed intake. However, supplementation decreased enteric methane production as a percent of gross energy intake.
The enteric methane of the steers fed DDG were somewhat lower than the steers fed cottonseed meal, he said.
Another two studies looked at cattle grazing on wheat pasture, which were then fed supplements. These steers were fed an energy supplement of steam-flaked corn, wheat midds, mineral and molasses.
As with the first study, methane and carbon dioxide levels of the steers were measured.
The results of the wheat grazing studies show methane, as a percent of gross energy intake, was decreased by 16% to 21% with corn-based energy supplementation. Methane emissions per kilogram of dry matter intake were decreased 18.5% to 20.5% with the corn-based supplementation.
While these studies are promising and energy supplementation offers potential to decrease methane emissions from grazing cattle, Cole pointed out more research is needed.
"This may include how much fat is [in] that supplement, the starch, the digestible fiber, the use of ionophores and there are some new potential methane inhibitors that may be coming onto the market in next few years," Cole said.
Other factors that could have an effect on research into how much supplementation could control GHG emissions includes certain grazing management techniques as well as forage quality, he said..
Russ Quinn can be reached at firstname.lastname@example.org
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