BARNHART, Mo. (AP) – A collapse in milk prices has wiped away the profits of dairy farmers, driving many out of business while forcing others to slaughter their herds or dump milk on the ground in protest. But nine months after prices began tumbling on the farm, consumers aren’t seeing the full benefits of the crash at the checkout counter.

The average price for a gallon of milk at grocery stores last month is down just 19 percent from its peak of $3.83 in July. Farmers, on the other hand, got $1.04 a gallon in April – 35 percent less than they were paid last fall. This winter, wholesale prices were down as much as 45 percent.

Price disparities are a fact of life both for farmers and anyone who shops at a supermarket, but the nature of milk – how it’s stored, priced and sold around the world – makes the gap all the more dramatic. In fact, the price that farmers get has been wildly volatile for years, creating a succession of booms and busts felt from pastures to the grocery store.

With each turn, proposals are floated to end the pricing seesaw, which at one extreme squeezes the profits of farmers and the other squeezes dairy processors. Any fix that boosts the price of milk runs the risk of bumping up how much consumers pay, too.

Today, frustrations are spilling over as the price crash creates widely divergent fortunes within the milk industry, boosting profits for the middlemen like dairy processors while pushing farmers to the edge of bankruptcy.

At the heart of the problem is the nature of milk. Unlike grain farmers who can hold out for better prices by storing crops in a silo, dairymen must sell raw milk to processors or else it spoils. And cows keep producing whether the economy’s expanding or in recession.

The price paid by processors to farmers is set by the U.S. Department of Agriculture based on commodity markets, which rise and fall with global demand.

U.S. milk exports soared last year and demand grew in countries like China while supplies dropped from Europe and Australia. U.S dairy exports jumped to $3.82 billion, or 11 percent all milk production in 2008 according to the U.S. Dairy Export Council. Wholesale prices jumped.

Dairies responded to the demand by increasing production. But once the global recession accelerated last fall, demand, particularly exports, fell off a cliff.

U.S. farmers were suddenly faced with too much milk and too many cows. Wholesale prices crashed. Farmers found themselves spending more to maintain their herds than they were being paid for raw milk.

”It’s an inequity that cries out for attention, consideration and action,” said Sen. Robert Casey, a Democrat from the dairy stronghold of Pennsylvania. Casey projects that 25 percent of his state’s 7,400 dairy farms could disappear because of the crisis.

Casey said most lawmakers are focused on short-term solutions – loans or subsidies – to help farmers bridge the period of depressed prices. But he said Congress should also explore why processors and retailers are keeping their prices high while wholesale prices collapse.

Farmers also are lobbying for a bill that would change the USDA pricing system for milk so that wholesale prices reflect what they pay for feed, fuel and other supplies.

If that happens, milk would be the only commodity of its kind to have a government-set price determined in part by the cost of production, said Scott Brown, dairy analyst at The University of Missouri’s Food and Agricultural Policy Research Institute.

”Anytime you put in place a policy that raises farm-level prices, those are going to get passed along to the consumer,” he said.

U.S. Secretary of Agriculture Tom Vilsack also said he is not eager to remake the USDA milk pricing program. Instead, he wants to see if a range of recent actions might buoy wholesale prices. USDA recently donated 500,000 pounds of excess powdered milk to needy countries to reduce U.S. supplies, and a new program will pay farmers to slaughter more than 100,000 dairy cows.

Some farmers say faster action is needed. They’re dumping their milk on the ground to draw attention to the crisis.

Jan Morrow, a farmer in Cornell, Wis., dumped milk on May 4 to protest the lowest whosesale prices she’s seen in 25 years of farming. If prices don’t rise, she says she may have to sell her cows.

Eddy Lekkerkerk, a 42-year-old dairy farmer outside Filer, Idaho, planned to participate in another milk dump on May 31. But he fears he may not be in business that long. For five months, he hasn’t made payments on the roughly $800,000 he borrows annually to buy feed for his herd of 1,000 cattle. He said his bank is forcing him to sell his herd to pay his debt.

He predicted many of his neighbors will have no choice but to follow him off the farm.

”It’s going to be ugly. This is historic stuff going on,” he said. ”The dairymen are nervous, and they are scared.”