Animal protection advocates are pressing Congress to increase penalties for interstate commerce involving cockfighting, a blood sport that continues to be widespread even though it is banned in most of the country.

Only two states — New Mexico and Louisiana — have no state laws against the competition, where specially bred roosters fight to the death or until there is a clear loser. Cockfight attendees usually place side bets on their favorites.

States with misdemeanor penalties — which usually amount to a small fine, but sometimes are punishable by up to a year in jail — tend to give prosecution a low priority, according to the Humane Society of the United States.

As a result, the Humane Society and more than 50 other animal protection groups are asking Congress to make the interstate transportation of fighting cocks (currently a misdemeanor) a felony punishable by up to two years in prison per offense.

“We think the felony penalty will deter people from trying to go to a cockfight,” said Wayne Pacelle, national president and CEO of the Humane Society. The organization has received reports of cockfights in about 25 states.

Other supporters of the bill are the National Chicken Council, which represents the commercial poultry industry, and more than 300 law enforcement agencies across the country. The Chicken Council has written members of Congress that shipping fighting roosters around the country for matches could spread a couple of harmful diseases to commercial flocks, including exotic Newcastle disease and avian influenza.

The Senate passed a bill in April making interstate commerce in fighting cocks a felony, but the House has taken no action on the proposal. Time is running short for action this year, with only a few more weeks left on the legislative calendar when lawmakers return to work after Labor Day.

Led by the United Gamefowl Breeders Association, based in Ripley, Miss., game-bird breeder associations have paid lobbyists more than $600,000 since 1999 trying to defeat bills that would increase penalties against cockfighting, according to federal lobbying records.

Larry Mathews, a spokesman for the breeders association, said states — not the federal government — should decide whether to restrict cockfighting and to what extent.

While emphasizing that his group opposes illegal cockfighting, Mathews suggested there is no victim or harm in the activity.

In studies by the University of California, Davis, and the University of Washington, “neither group was able to prove that poultry can even feel pain. We feel that the reality of the matter is there is no victim” in legal cockfighting, Mathews said. He said he did not have copies of the studies and could not recall the names of researchers involved.

Joy Mench, a professor of animal science at the University of California, Davis, said she was not familiar with a university study similar to what Mathews described.

“There’s ample proof that birds feel pain,” Mench said.

A University of Tennessee professor of animal science in Knoxville, Kelly Robbins, agreed. “Chickens’ beaks and skin are full of pain-sensitive nerves,” Robbins said. “All the evidence that I am aware of suggests that chickens have a very highly developed sense of pain.”

The federal government should focus on more important matters, such as child abuse, rather than penalize game-fowl breeders, most of whom are just trying to continue a long line of roosters known for their colorful plumage and to exhibit them at shows, Mathews said.

About 40 percent of the game fowl are exported, Mathews said. The bill would also make the export of roosters for fighting purposes a felony.

“I don’t see where the United States has the right to create a crime for what happens to a chicken in Mexico City,” Mathews said.