Livestock that feed on spent brewery grains are some of the happiest animals around.

"Cows love the stuff," said Main Street Brewery brewmaster Brandon Miller. "When the truck rolls up, they gallop over."

The Main Street Brewery in downtown Cortez generates an estimated 12,000 pounds of grain by-product annually from its 10-barrel brewery. All the spent grain is donated to area ranchers and reused as livestock feed.

"It's 100 percent recyclable," Miller said.

The local business is not alone. According to a 2013 Brewers Association survey of its members, brewers resell or give away nearly 90 percent of their spent grain as livestock feed.

A new proposal by the Food and Drug Administration, however, could demand brewers to dump spent grains at landfills.

"It would be absolutely ridiculous to force us to take the grain to the landfill," Miller said.

Mark Youngquist, owner of the Dolores River Brewery, also disagrees with the plan. He donates 600 to 800 pounds of brewing grain per week to area farmers and ranchers.

"It is the highest-grade barley out there and makes excellent livestock feed because it is so high in protein," he said. "Brewers passing it off to ranchers is a symbiotic relationship that has worked for a thousand years without a problem."

The FDA proposal would require brewers to meet the same standards as other livestock and pet-food manufacturers, imposing new handling procedures, record-keeping and other food safety processes on brewers.

Sen. Mark Udall, D-Colo., a member of the U.S. Senate Small Brewers Caucus, contends that the new directive may unjustifiably hurt Colorado's brewers and farmers.

In a letter to FDA officials, he wrote that the U.S. Department of Agriculture has decades of data that demonstrate use of spent grain used as livestock feed.

"This information does not reveal, to my knowledge, any evidence that dedicating spent brewers grains for agricultural use has ever compromised food safety to animals or humans," Udall wrote. "Partnership between brewers and farmers is longstanding, and it allows for an environmentally responsible way to dispense with an otherwise useless by-product."

A strong proponent of Colorado's job-creating craft breweries, Udall argues that brewers' spent grains, whose sugars are fermented to make craft beer, are an economical and high-protein food source for beef and dairy cattle.

"When brewers succeed, so do countless other businesses and sectors of our economy," Udall said in a press release last week.

John Carlson, executive director of the Colorado Brewers Guild, said the costs of complying with the proposed federal regulations would be higher than the cost of sending spent grain to a landfill.

"Thoughtful reuse of spent brewers grain is elegant and efficient," he said. "Increased costs for Colorado brewers and Colorado ranchers and wasted food for livestock is not a good way to move forward."