New USDA regulations announced Tuesday will require dog breeders who sell pets online, by mail or over the phone to apply for federal licenses.

Until now, many breeders who run their business online have avoided the licensing and inspection requirements that affect breeders who sell to pet stores.

Commercial pet stores don't require licenses because buyers can see the animals before they buy them and determine if they appear healthy.

"There are hundreds of thousands of dogs languishing in small wire cages, denied vet care and exposed to the elements that literally had no protection under federal law," Wayne Pacelle, president of The Humane Society of the United States, told The Associated Press. "This turns that around."

Adopting the measure headed off the bipartisan Puppy Uniform Protection and Safety Act, or “PUPS Act,” which sought to modernize the Animal Welfare Act passed in 1966.

The new regulations affect dog, cat and rabbit breeders with more than four breeding females and require them to apply for a USDA permit, pay an annual licensing fee and consent to random inspections.

The USDA estimates that up to 4,640 dog breeders could be affected by the rules, along with 325 cat breeders and up to 75 rabbit breeders.

Kevin Shea, administrator of the USDA's Animal and Plant Health Inspection Service, says the new rules — which go into effect in 60 days — are in response to a 2010 USDA inspector general’s report that uncovered deplorable conditions at breeding facilities across the nation.

Often referred to as puppy mills, such facilities are characterized by overcrowded cages, grisly conditions and unhealthy animals. USDA inspectors cited numerous reports of buyers who received animals that were sick or dying.

Shea said the licenses will cost $750 or less and that complying with USDA regulations will only be pricey for breeders who aren't already ensuring their animals are properly cared for.

Still, some breeders lobbied against the changes, saying the rules could run them out of business.

Lisa Petersen, a spokeswoman for the American Kennel Club, said the rules are "overly broad and will do more damage than good."

The group argues that the term “breeding female” is vague and may prevent some small breeders from keeping dogs in their homes.

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