Demand is on the rise for rescued Hunter Valley donkeys to protect stock from being maimed or killed by wild dogs.

Wild dogs are considered so devastating across New South Wales that scientific officials have declared them a key threatening process.

Farmers lose millions of dollars each year and now they are turning to donkeys, which are notorious for fending off dogs.

The Good Samaritan Donkey Sanctuary in the Hunter Valley has taken to pairing donkeys with desperate farmers like Mike O'Brien.

Mr O'Brien travelled from Queensland to get his donkeys Milo and Coco.

He says he has lost no sheep since they started work.

"I've tracked dingoes going flat across a paddock and seen the donkey tracks after them," he said.

"The dogs have taken-on an electric fence. So they really stick the skids on under the dogs if they turn up in your area - and they do kill dogs.

"I've had all the donkey/ass jokes told to me and it's like water off my back.

"I'm marking 100 per cent lambs again, so I'm smiling."

Mr O'Brien says donkeys are tough, bond well with stock and live up to 40 years.