The study, which was published in the Journal of Animal Science, looked at greenhouse gas emission from beef cattle during different life stages. They found that the ‘cow-calf’ stage - which is from birth until the calf is six to ten months old - is the biggest contributor of greenhouse gases.
The scientists said this is because the cow eats plants like hay and grasses while nursing calves, which can be used more effectively by the methane-producing bacteria in a cow’s gut than the corn and grains which feedlot cattle eat.
“If you look at everything that contributes to greenhouse gases through the beef supply chain, then it is the cow-calf that produces the greatest greenhouse gases,” said co-author Frank Mitloehner, an associate professor in the Department of Animal Science at UC Davis.
“The more roughage is in the diet of the ruminant animal, the more methane is produced by the microbes in the gut of the ruminant, and methane comes out the front end.”
Mitloehner added that further greenhouse gas reductions could be achieved by using growth promotants in beef cattle, but consumers remain resistant to these new technologies.
“The technologies many consumers are critical of are those that help us receive the greatest environmental gains,” he explained.