RSPCA shelters across the state are operating at capacity for dogs for the first time since changes to the law in 2017.

Legislation restricted pet shops to selling dogs and cats sourced from shelters, pounds, or enrolled foster carers, resulting in fewer dogs and cats being bred.

"While dogs and cats make up the majority of the animals in our care, RSPCA Victoria is currently operating at capacity for all animals," Victoria animal care manager Nadia Peiris said.

"The public can help us by coming into our shelters to adopt dogs, cats, rabbits or guinea pigs."

The RSPCA is offering dog adoptions for $100 on Saturday, August 20.

The organisation hopes the drive will go some way to encouraging more adoptions, as shelters see fewer people coming in to reclaim stray and lost animals, a drop in adoption applications, and more animals requiring retraining.

"For us, it really is a perfect storm that is impacting our ability to move animals into their forever homes, which we know is the best place for them," Ms Peiris said.

More than 70 dogs are up for adoption at The Lost Dogs' Home sites in North Melbourne and Cranbourne, prompting the shelter to also slash its fees for a week from Friday, August 12.

The reduced adoption fees will apply to most dogs, and go down from $530 to $195 at the shelters.

Winter is a typically slower time for adoptions, the home says, but this year's drop has been compounded by the rising cost of living and owners no longer having time to care for their animals.

"We haven't seen these kinds of numbers in a very long time and possibly in a decade,'' the home's Suzana Talevski said.

"'While we are desperately trying to place as many of these beautiful animals in foster care while they wait for their perfect match, we would much prefer they were in a permanent and loving home.'"

Owners are also surrendering their pets because of property restrictions on animals, along with the lack of time they have to spend with them, and animal behavioural issues.

The organisation has urged shelter visitors to be patient during the week of slashed prices.

Australian Associated Press