HARRISBURG - In 2008, Gov. Rendell signed the state's new dog law, proclaiming it the toughest in the country governing commercial breeding kennels, which sell thousands of puppies to pet shops each year.

Now a standoff between the Rendell administration and animal welfare advocates over the use of wire flooring in cages is threatening final approval of the law's regulations for the 100 commercial kennels that remain in Pennsylvania.

The Independent Regulatory Review Commission will hear public testimony Thursday before approving or rejecting the law's 873 pages on conditions in commercial kennels.

Rendell administration officials will be defending what they call "a gap" in the law involving cage flooring. The law requires adult dogs to have solid flooring in cages, but allows puppies under 12 weeks to stand on wire flooring.

That means adults bred twice a year could end up living on wire through pregnancy and nursing for up to six or eight months a year, which opponents argue violates the spirit and letter of the law.

Chief among the law's provisions was the "elimination" of wire flooring, used in the oversize rabbit hutches popular in most kennels because they are easier to clean. Wire is blamed for painful paw abrasions, cysts and splayed feet on animals that spend years in such cages.

The prospect of dogs' continuing to spend even part of their lives in cages without solid flooring is unacceptable to the legislation's lead sponsor.

"The administration is circumventing the intent of the dog law," said Rep. James E. Casorio (D., Westmoreland). "I don't understand why they would try to harm the very animals it was supposed to protect."

Administration officials acknowledge recently discovering a "gray" area in the law and have sought to address it by requiring 50 percent of the nursing mothers' cages to have solid flooring.

"I don't think there's a controversy," Rendell said in a recent interview. "I'd never let dogs stand on wire day after day after day. They will find their way to the wood floor."

Rendell's rescued dog, Maggie, was pulled from a wire-floored rabbit hutch in 2008.

Karen Overall, a member of the governor's Canine Health Board, which was charged with drafting and approving the regulations, called the administration's revised proposal "deplorable," arguing that wire for any dog under any circumstances leads to long-term physical and behavioral problems.

Marsha Perelman, a member of the Dog Law Advisory Board, said that if the regulations in their entirety were voted down, including those governing temperature extremes, dogs in breeding kennels would continue to be at risk of life-threatening conditions.

The number of commercial kennels, defined as those selling or transferring more than 60 dogs or selling any dogs to pet stores, has fallen from 300 to just over 100 since the law took effect in 2009.

The lobbyist for the Pennsylvania Professional Dog Breeders Association did not respond to several requests for comment.