In July, Dannon introduced its first yogurts made with non-GMO ingredients and announced its intention to build on the introduction with additional non-GMO choices for consumers.

Related: What makes people queasy about GMO foods?

What is sustainable? Dannon says it's going to source milk from cows fed non-GMO feed beginning next year for its three flagship brands. Six ag groups write letter saying non-GMO feed isn't sustainable. (Photo: Karisssa/Thinkstock)

The company also said it was going to label all Dannon products in the U.S. that have GMO ingredients. Next year, the company plans to start a two-year process to ensure that the cows that supply milk for Dannon’s three flagship brands: Danimals, Oikos and Dannon, are fed non-GMO feed, which is a first for a non-organic yogurt maker. Dannon estimated this process would involve the conversion of an estimated 80,000 acres of farmland to produce non-GMO crops in order to provide feed for the cows who provide the milk to make the products.

“Shoppers are our main ingredient, and what is important to them drives what we do. For this reason, the range of products we make is evolving to provide even more choices,” said Mariano Lozano, CEO, Dannon, in a media statement.

Lozano said the labeling added to transparency, which is the first step in the Dannon Pledge, where Dannon commits to improving sustainable agriculture practices around its milk supply, increasing transparency of its portfolio of products and evolving to more natural and fewer ingredients for its flagship Dannon, Danimals and Oikos brands, which account for about half of the company’s sales.

“Choosing to purchase foods with fewer or more natural ingredients, or with or without GMO ingredients, is an important individual decision, and we feel strongly that people have the right to know how companies are making food. This is just the first of many steps towards our continued transparency and one that we hope others will follow,” said Lozano.

Related: Obama signed GMO labeling bill

Today, leaders six farm organizations — the American Farm Bureau Federation, American Soybean Association, American Sugarbeet Growers Association, National Corn Growers Association, National Milk Producers Federation and U.S. Farmers and Ranchers Alliance – mailed a letter to Lozano disputing the company’s sustainability claims.

“In our view, your pledge amounts to marketing flimflam, pure and simple,” the letter reads. “It appears to be an attempt to gain lost sales from your competitors by using fear-based marketing and trendy buzzwords, not through any actual improvements in your products.”

The six groups say that during the last 20 years, advancements in agricultural technology have allowed farmers to use less pesticides and herbicides, fossil fuels, and water, and prevent soil erosion. Taking away GMOs is akin to turning back the clock and using outdated 20th century technology to run a business, they argue.

"This is just marketing puffery, not any true innovation that improves the actual product offered to consumers," said Randy Mooney, chairman of the National Milk Producers Federation, and a dairy farmer from Rogersville, Missouri, in a media statement. "What's worse is that removing GMOs from the equation is harmful to the environment - the opposite of what these companies claim to be attempting to achieve."

Numerous studies have come out over the last 20 years proving the safety of GMO food and the environmental benefits of growing GM crops, yet skeptics remain. In a recent study, 37% of Americans said GMO food was safe to eat.

Related: Scientific Advisory Panel to meet Oct. 18-21 to talk glyphosate