The American Farm Bureau Federation, a slate of livestock groups and several veterinarian organizations are mounting a last-minute push for a farm bill provision preempting state-level animal confinement laws.

The National Pork Producers' Council joined with AFBF and beef, pork, dairy, sheep and turkey groups Tuesday in a letter to House Agriculture Committee leaders backing language addressing California's Proposition 12 and similar ballot initiatives. They argue that allowing Proposition 12 to continue threatens relationships with trade partners and could result in "arbitrary and conflicting state laws across all 50 states, on any myriad of issues."

"If Congress fails to act, the chaos from a segmented market will drive consolidation and force American family farmers out of business, as the rest of agriculture remains exposed," the groups wrote.

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The American Association of Swine Veterinarians and the American Veterinary Medical Association sent similar letters on Tuesday.

House Agriculture Committee Chair Glenn Thompson included language in his draft farm bill that would prevent state and local governments from imposing standards on livestock produced outside of that state. It would apply to any domestic animal raised for slaughter or human consumption, with the exception of eggs.

Opponents of the provision are pushing to get it removed from the bill, which the committee will consider on Thursday.

Wayne Pacelle, the president of Animal Wellness Action, said the provision makes the farm bill a "partisan bill with just a very narrow slice of Republicans actively backing it." He pointed to previous letters from conservative opponents.