Horses could soon be butchered in the US for human consumption after Congress quietly lifted a five-year-old ban on funding horse meat inspections, and activists say slaughterhouses could be up and running in as little as a month.

Slaughter opponents pushed a measure cutting off funding for horse meat inspections through Congress in 2006 after other efforts to pass outright bans on horse slaughter failed in previous years.

Congress lifted the ban in a spending bill President Barack Obama signed into law November 18 to keep the government afloat until mid-December.

It did not, however, allocate any new money to pay for horse meat inspections, which opponents claim could cost taxpayers $3 million to $5 million a year.

The US Department of Agriculture would have to find the money in its existing budget, which is expected to see more cuts this year as Congress and the White House aim to trim federal spending.

The USDA issued a statement Tuesday saying there are no slaughterhouses in the US that butcher horses for human consumption now, but if one were to open, it would conduct inspections to make sure federal laws were being followed. USDA spokesman Neil Gaffney declined to answer questions beyond what was in the statement.

Although there are reports of Americans dining on horse meat a recently as the 1940s, the practice is virtually non-existent in this country, where the animals are treated as beloved pets and iconic symbols of the West.

The last US slaughterhouse that butchered horses closed in 2007 in Illinois, and animal welfare activists warned of massive public outcry in any town where a slaughterhouse may open.

"If plants open up in Oklahoma or Nebraska, you'll see controversy, litigation, legislative action and basically a very inhospitable environment to operate," predicted Wayne Pacelle, president and chief executive of The Humane Society of the United States.

But pro-slaughter activists say the ban had unintended consequences, including an increase in neglect and the abandonment of horses, and that they are scrambling to get a plant going – possibly in Wyoming, North Dakota, Nebraska or Missouri.

They estimate a slaughterhouse could open in 30 to 90 days with state approval and eventually as many as 200 000 horses a year could be slaughtered for human consumption.

Most of the meat would be shipped to countries in Europe and Asia, including France and Japan.

Dave Duquette, president of the non-profit, pro-slaughter group United Horsemen, said no state or site has been picked yet but he's lined up plenty of investors who have expressed interest in financing a processing plant.

While the last three slaughterhouses in the U.S. were owned by foreign companies, he said a new plant would be American-owned.

"I have personally probably five to 10 investors that I could call right now if I had a plant ready to go," said Duquette, who lives in Hermiston, Oregon. He added, "If one plant came open in two weeks, I'd have enough money to fund it. I've got people who will put up $100 000."

Sue Wallis, a Wyoming state lawmaker who's the group's vice president, said ranchers used to be able to sell horses that were too old or unfit for work to slaughterhouses but now they have to ship them to butchers in Canada and Mexico, where they fetch less than half the price.

The federal ban devastated "an entire sector of animal agriculture for purely sentimental and romantic notions," she said.

Lawmakers in California and Illinois have banned the slaughter of horses for human consumption, and more than a dozen states tightly regulate the sale of horse meat.

Federal lawmakers' lifting of the ban on funding for horse meat inspections came about in part because of the recession, which struck just as slaughtering stopped.

A federal report issued in June found that local animal welfare organisations reported a spike in investigations for horse neglect and abandonment since 2007.

In Colorado, for example, data showed that investigations for horse neglect and abuse increased more than 60% - from 975 in 2005 to almost 1 600 in 2009.

The report from the US Government Accountability Office also determined that about 138 000 horses were transported to Canada and Mexico for slaughter in 2010, nearly the same number that were killed in the US before the ban took effect in 2007.

The U.S. has an estimated nine million horses.