NEW YORK – The American Farmers for the Advancement and Conservation of Technology has started a counteroffensive to stop the proliferation of milk that comes from cows not treated with synthetic bovine growth hormone.

The group says its grassroots organization came together to defend members’ right to use recombinant bovine somatotropin, also known as rBST or rBGH, an artificial hormone that stimulates milk production. It is sold by Monsanto under the brand name Posilac, The New York Times reports.

A growing number of consumers choose milk that comes from cows not treated with the artificial growth hormone. Even though the U.S. Food and Drug Administration has declared the synthetic hormone safe, many other countries have refused to approve it, and many consumers have lingering concerns about its impact on health and the welfare of cows.

Retailers from Whole Foods Market to Wal-Mart Stores sell milk that is labeled as coming from cows not treated with the hormone. The trend might not stop with milk, as Kraft is planning to sell cheese labeled as having come from untreated cows.

But consumer demand for more natural products has conflicted with some dairy farmers’ desire to use the artificial hormone to bolster production and bottom lines, and it has certainly interfered with Monsanto’s business plan for Posilac.

Cows typically produce an extra gallon a day when they are treated with Posilac. That can translate into serious money for dairy farmers at a time when prices are near record highs.

The group is meeting with retailers and pushing efforts by state legislators and state agriculture commissioners to pass laws to ban or restrict labels that indicate milk comes from untreated cows.