SALT LAKE CITY — From corn fields to Wall Street, enthusiasm for ethanol is at an all-time high. But not everyone is enthusiastic.

Demand for the corn-based fuel is driving up the cost of feed corn, making it more expensive to feed cows, chickens, and pigs.

“It’s hard to see where the future is, if corn keeps going up,” a cattle rancher in southwestern Wyoming, Kerby Barker, said. “Anytime you jack up the price of fuel, anytime you jack up the price of corn, it just drives up our bottom line.”

Long-term, it could drive up the cost of food, which is alarming to meat producers and food companies.

Like many ranchers, Mr. Barker questions the 51-cent-a-gallon tax credit created by Congress to encourage growth of the ethanol industry. While the subsidy expires in 2010, lawmakers introduced a bill last week that would make it permanent.

A potential split is in evidence this week in Salt Lake City during the annual meeting of the country’s largest general-interest agriculture group, the American Farm Bureau Federation. Its members still are trying to understand the consequences of the nation’s rapid expansion of ethanol.

“We have a bull on the loose here, and it’s going to have a lot of implications for American agriculture and our population,” the Agriculture Department’s chief economist, Keith Collins, told Farm Bureau members yesterday.

Enough plants are under construction or being expanded to more than double the nation’s ethanol production, from around 5 billion gallons now to 11 billion gallons, according to industry estimates.

The ethanol boom has been good news for grain farmers and rural communities, where new plants are opening at a breakneck pace. While big agribusiness companies such as Archer Daniels Midland Co. and Cargill Inc. produce the most ethanol, many new plants are farmer-owned cooperatives.

But the boom has put the squeeze on those who produce beef, chicken and pork.

“The big thing is much, much bigger feed costs, and that will give us red ink, I’m afraid, in 2007 and 2008,” an agriculture economist at the University of Missouri, Ron Plain, said.

High corn prices are affecting the margins for meat producers such as Smithfield Foods Inc. and Tyson Foods, which have seen earnings fall.

Eventually, sustained high corn prices will probably lead to higher grocery bills. If corn prices rise by $1 a bushel, within a couple of years, grocery shoppers should see the price of pork rise 3% to 3.5%, Mr. Collins said.

But food companies say the impact still goes beyond meat and milk. High prices prompt farmers to plant corn in place of other crops, such as wheat, driving up the price of things like wheat flour, said Cal Dooley, who heads the Food Products Association, an industry group. The food companies Mr. Dooley represents want to tie the subsidy to market forces, raising it when prices are low and lowering it when prices are high.

The question is whether the industry has grown enough to survive without the subsidy, according to the Agriculture Department economist, Mr. Collins. There have been periods in the past year where ethanol was profitable without the subsidy, and periods when it was not, he said.