Filed last week with the US Department of Agriculture (USDA), the complaint states that Horizon Organic is violating a number of provisions under the National Organic Program (NOP).
According to the Cornucopia Institute, an agricultural policy research group that filed the complaint, Horizon is not providing sufficient pasture for its cattle, and is not maintaining livestock living conditions that accommodate the health and natural behavior of the animals.
However, Horizon Organic, a unit of Dean Foods, has said that the allegations are "completely without merit".
"We work closely with our certifiers on an ongoing basis to ensure that each dairy is fully certified organic and meets the USDA national organic standards, which are the most stringent in the world," it said in a statement.
The recent complaint is the fourth of its kind filed by Cornucopia over the past 20 months. The non-profit organization, which was set up in 2004 to support family-scale organic farmers, has filed three previous complaints against another industry giant, Aurora Organic Dairy. One of these was dismissed by the USDA, a second is under investigation, and the third is being reviewed. The USDA said it is also currently reviewing the latest complaint received last week.
According to Cornucopia, Dean Foods is currently operating an 8,000 cattle farm in Idaho, where an arid climate does not allow for sufficient pasture. And in its farm in Kennedyville, Maryland, cattle are prevented from accessing good pastureland, claimed the group.
It added that the company had created an "illusion" of pasturing by "temporarily" putting its cows on green fields for VIP visitors.
However, Horizon claims to be "transparent in its practices" and said it welcomes a USDA review should one be forthcoming.
Cornucopia is supported in its claims by the public interest organization Organic Consumers Association (OCA), which is encouraging a boycott of Horizon and Aurora organic dairy products. The OCA cites a scorecard released by Cornucopia in April, which rates the nation's organic dairy brands according to integrity of organic farming practices.
The scorecard, found here , fails both Horizon and Aurora dairy production as "ethically challenged".
However, other organic dairy firms that received an "excellent" rating in the scorecard have expressed their concerns over the complaint filed by Cornucpia.
Organic Valley told FoodNavigator-USA.com that it "absolutely does not support what Cornucopia is doing with its complaint to the USDA about Horizon and Aurora."
"We do not support the boycott. We are discouraged and unhappy about how Cornucopia is handling this matter. It is not to the advantage of the organic industry to handle things in this way," it said.
But Cornucopia senior farm policy analyst Mark Kastel claims the group is acting as an organic watchdog, assuring that no compromises to the credibility of organic farming methods and the food these produce are made in the pursuit of profit.
And while this means that small-scale farmers are the most likely to receive the group's support, it does not exclude larger-scale operations.
"This is not a debate of small farmers versus big farmers. It's ethical farmers versus farmers that are willing to compensate the ethics of organic farming," said Kastel.
"Some farmers are going to extra effort, many have lower herd production because of organic constraints, and they are placed at a competitive disadvantage."