The New South Wales Premier has thrown his support behind an idea that would see convicted arsonists help farmers destroy animals injured in bushfires.

Yesterday, three teenagers were charged with arson after a fire in Sydney's west burnt 10 hectares of bushland.

The 14-year-old and two 15-year-olds have been granted conditional bail.

Speaking at a bushfire press conference at Bookham in southern New South Wales, Barry O'Farrell said new laws are needed to stop arsonists.

"I met the mayor of Yass - she's not been able to be here because her property is one of those that's in the line of the fire - she had a great suggestion," he said.

"We ought to bring this people down here to districts like this and have them assist is putting to death those sheep that have been injured in these fires.

"Because if you did that once you would never ever want to see it again."

The Premier says he will talk to the state's Attorney-General about the plan.

"We now in this state have graffiti offenders out there removing their vandalism," he said.

"The idea of ensuring that arsonists have to get out there and confront what fires can do to properties, to animals, and regrettably to humans, isn't a bad thing either."

The RSPCA's state chief Steve Coleman has given in-principle support to the plan.

He says it is a great idea, as long as the arsonists are not themselves doing the culling.

"It's our view that it really takes the ability of the person to do it to do it properly and that's why suggesting that juveniles actually conduct the process of euthanasia may not be the best thing," he said.

"But we would be very happy to have those people involved, to shadow our staff in doing what is ultimately a very very distressing and awful job."

The Department of Primary Industries estimates about 10,000 head of sheep and cattle have been lost state-wide.