The cobalt scandal is the best thing to happen to Melbourne's veterinary industry after years of skirting the rules of racing, a vet says.

Dr Stuart Vallance told a cobalt inquiry there had been a bad culture among Melbourne vets for years, even before cobalt became an issue.

"There's been a big culture in veterinary medicine in Melbourne that if you don't get a positive swab and you're not caught, you're not breaking the rules. That's part of the problem," Vallance said.

"This cobalt case has been the best thing that's ever happened in veterinary practice in Melbourne."

Vallance used to work for Flemington Equine Clinic, which has been caught up in cobalt cases involving Melbourne trainers Danny O'Brien and Mark Kavanagh and Kavanagh's son, Sydney trainer Sam Kavanagh.

There have been a lot of questionable practices in the industry over the years, Vallance told O'Brien and Mark Kavanagh's appeal against their cobalt disqualifications.

"The veterinarians need to take a stand on vets as a whole because there's been a lot of questionable practices over the years, questionable substances being sold and vets are to blame for a fair bit of it."

Vallance said trainers also got caught up in the culture.

"If you're not using a substance you're not winning," he told the Victorian Civil and Administrative Tribunal on Monday.

"If you're not winning you don't get the returns, you don't get owners. Before you know it you're gone."

Vallance left Flemington Equine after senior partner Dr Tom Brennan came clean in July last year that he had added a substance called vitamin complex to drips given to some of O'Brien and Mark Kavanagh's horses.

Brennan has named former Flemington Equine vet Dr Adam Matthews as the supplier of the vitamin complex, which Matthews denies.

One of the bottles Brennan sent to Sam Kavanagh in Sydney was found to contain cobalt.

Sam Kavanagh said Brennan, a close friend, told him Melbourne stables were successfully using the vitamin complex.

He agreed with Racing Victoria barrister Jeff Gleeson QC that Brennan told him that his father and O'Brien were using it.

Sam Kavanagh, who was disqualified last year by NSW stewards, said he trusted Brennan.

"I had total faith in him. I made a huge error of judgment. I've been punished for it," he said.

Flemington Equine practice manager Aaron Corby denied trying to cover up the clinic's involvement or that he and Brennan tried to pressure Sam Kavanagh not to reveal it supplied the vitamin complex.

Sam Kavanagh is back at VCAT on Tuesday before witnesses give evidence on the key appeal issue of whether labs were properly accredited to test for cobalt at the time.