SALEM - A bill to crack down on "puppy mills" by setting a limit of 50 breeding dogs at production facilities won final approval Tuesday in the Oregon Senate.

The measure goes to the governor, who is expected to sign it. It is aimed at putting out of business large-scale breeding operations where dogs at times have been subjected to cramped, filthy conditions.

Backers say six such operations have been busted by animal enforcement officers in Oregon over the past two years and that the bill is aimed at shutting down similar ones.

"Clearly, we've got a problem in Oregon. This legislation is an important first step toward shutting them down and stopping their proliferation in the state," said Scott Beckstead, Oregon director for the Humane Society of the United States.

The bill, which also sets minimum care standards, including exercise time for dogs, is part of a wider push to rein in inhumane breeding operations around the country.

Some senators argued against the 50-dog limit, saying it didn't ensure quality care and could harm some responsible dog breeders.

"You can have a state-of-the-art facility for hundreds of dogs with lots of staff and high-quality care, or you can have the owner of a single dog who is extremely abusive," said Sen. Fred Girod, R-Stayton.

However, the Senate voted 18-10 to send House Bill 2470 to Gov. Ted Kulongoski after backers said the new law will not affect most hobby breeders.

Other supporters cited the squalid conditions that authorities found at some Oregon puppy mills.

"They're not treated like pets; they're treated like cash crops," said Sen. Diane Rosenbaum, D-Portland. "Hundreds of dogs were discovered living in filthy, crowded and inhumane conditions."

Among other things, the measure would require retail pet stores to provide information about a puppy's medical and breeding history and would set conditions allowing refunds if the dog suffers a disease or congenital disorder.

Louisiana, Pennsylvania and Virginia approved laws last year to curtail puppy mills, according to the Humane Society of the United States. This year similar laws were passed in Indiana as was one in Washington state, which Gov. Chris Gregoire signed.