A Sydney greyhound trainer has supported claims that up to 90 per cent of New South Wales trainers use live bait to "blood" the dogs and make them go faster.

Todd Fear gave evidence at the Special Commission of Inquiry into the Greyhound Racing Industry which is holding public hearings into allegations of serious animal abuse.

The allegations include live baiting to "blood" the dogs and the mass slaughter of thousands of greyhounds each year which are not fast enough to race.

The inquiry was sparked by the ABC's Four Corners program which in February aired allegations of live baiting in the industry.

Counsel Assisting the Commission Stephen Rushton SC in his opening address yesterday, described the practice as hideous.

Under questioning from Mr Rushton this morning, Mr Fear agreed with claims that live baiting of greyhounds - using live rabbits and other small animals - was "rampant".

When asked what he meant by rampant he said he believed 90 per cent of trainers in the industry did it.

Mr Fear: "It was just the way to do it," he said. "It wasn't policed was it?" Mr Ruston: "When you say it wasn't policed you mean it wasn't policed by Greyhound Racing NSW?" Mr Fear: "Yes". Mr Rushton: "And are you saying if it was policed the practice wouldn't have happened?" Mr Fear agreed.

Yesterday, internal documents from Greyhounds Australasia revealed to the inquiry the industry was responsible for the unnecessary deaths of anywhere between 13,000 to 17,000 healthy greyhounds a year.

The inquiry heard yesterday the RSPCA received a mere 410 greyhounds and managed to re-home just 154 of them over a six-year period.

The hearing has now been closed to the public while another witness gives evidence on camera.

The hearings are scheduled to run all week, with evidence from greyhound trainers and owners, and the state regulatory body Greyhound Racing NSW.