Hormone use may make dairy farming greener-US study

The research suggests that, if used on a large scale, bovine growth hormones could reduce the number of cows needed to produce milk, cutting demand for corn and soybeans and reducing greenhouse gas emissions by decreasing the amount of manure they produce.

Decomposing manure produces methane, a greenhouse gas. Scientists say controlling methane emissions from animals would help address climate change.

"All food production has an environmental impact, but many people don't realize that," Bauman said by telephone.

Bauman and colleagues used computer models to calculate the impact that greater use of growth hormones might have. They figured using the hormones would let 843,000 cows produce the same amount of milk now produced by 1 million.

That would save 491,000 tonnes of corn, 158,000 tonnes of soybeans, and total feed would be reduced by 2.3 million tonnes. The change would allow farmers to reduce the amount of cropland needed by 540,000 acres (219,000 hectares) and reduce soil erosion by 2.3 million tonnes a year, they said.

And it would reduce carbon dioxide emissions by 1.8 billion pounds (824 million kg), methane emissions by 90 million pounds (41 million kg), and nitrous oxide emissions by 210,000 pounds (96,000 kg).

Michael Hansen, a senior scientist with Consumers Union, said the study is based on a "false notion" that you can produce the same quantity of milk with less feed.

Hansen said Monsanto in the late 1980s sought to make a label claim that the product increased feed efficiency, but the FDA said the company did not provide enough evidence for that claim.

(Editing by Patricia Zengerle)