With South Australia's animal shelters overflowing, the holiday season is a great time to adopt an unwanted pet, the RSPCA says.

But the organisation warned people to avoid dodgy breeders and puppy farms.

Environment Minister Ian hunter echoed the RSPCA's calls for people to adopt from a shelter.

Mr Hunter and his family adopted a three-legged Staffordshire cross, called Bailey, from a shelter eight months ago.

"Bailey was sitting there forlornly in his cage," Mr Hunter said.

"He's a rather ugly looking dog and of course he's only got three legs and he'd been there for about 18 months or so and no one was wanting to adopt him.

"We normally adopt older animals that people normally don't want to adopt, but Bailey just kept on looking at us and we just couldn't go past."

Mr Hunter has encouraged people to follow his example if they are planning on getting a pet this Christmas.

"My plea is above all else, don't buy a pet from an inhumane puppy farmer, get one from a reputable breeder, or even better, go to an animal shelter like the Animal Welfare League or the RSPCA," he said.

RSPCA chief executive officer Tim Vasudeva said Christmas was a great time of year to adopt a pet, provided new owners were aware of the costs and responsibilities involved.

He said it is a busy time of year for the organisation, with three times as many animals in foster care than in winter.

"I think we have over 500 or 600 kittens in foster care at the moment, excluding the ones at our shelters," Mr Vasudeva said.

The RSPCA is hopeful changes in the law to make de-sexing and microchipping mandatory will help reduce the number of pets that end up in shelters.

Those laws are expected to be passed by Parliament next year.