The emaciated staffy cross mastif was starved and dehydrated, close to dying.

RSPCA officer Dianne McCance said this was the worst case of starvation she had seen in Whyalla.

Weighing 6.6kg, at least half his normal weight, Ms McCance said he looked about four-months-old.

The RSPCA kept him cool and gave him food and water, but he wasn't eating much at first.

But after a week of loving attention, he was eating and acting like a puppy should.

Although only early days, Ms McCance said he seemed a lot better and there was a small improvement in his weight.

She said it would be at least another three months before he was healthy, and he would then be put up for adoption.

Foster carer Louise Thompson will look after him during the Christmas period.

Ms McCance said she considered euthanising him but she just couldn't.

"He deserves a second chance," she said.

"Getting him a good home, that would be great."

Finding the story behind the puppy's case was hard, but Ms McCance said usually a puppy would be found or taken in before it got to this state.

"If you can't afford to feed them, come to the RSPCA, we give out food parcels as a one off," she said.

"Don't just leave the dog to starve, bring it here, don't give it away."

Ms McCance encouraged anyone who may recognise the dog to contact the RSPCA shelter.

"Because we would like to prosecute someone who's doing that to a pup."