Trainer Danny O'Brien has told his cobalt appeal hearing he deliberately withheld information because he did not trust Racing Victoria.

O'Brien and fellow trainer Mark Kavanagh are appealing their respective four and three year cobalt disqualifications before the Victorian Civil and Administrative Tribunal.

On Wednesday, O'Brien said he had not told RV stewards of a $3000 payment to vet Dr Tom Brennan from a personal bank account until July 21 last year although he had made it the previous November.

The payment was for a trial of an IV drip regime he said he thought contained vitamins and electrolytes to aid post-exercise recovery in horses.

Brennan was adding a substance called vitamin complex which was later found to contain a high level of cobalt.

O'Brien said the day after Brennan told stewards of the payment, a press release came out saying O'Brien and Kavanagh had each paid $3000 for vitamin complex.

"That's why I didn't tell the stewards (of the payment)," O'Brien said.

"I knew what occurred in the next 24 hours (chief steward) Terry Bailey would once again betray everyone's trust and use it publicly against myself and the other trainers despite giving an undertaking to Dr Brennan that those facts would not be disclosed until everyone had a chance to examine them."

Earlier the hearing was told O'Brien introduced the drips trial after Brennan told him leading Australian trainer Chris Waller was using IV drips to aid post-exercise recovery.

Previously O'Brien had been using a saline drench as a recovery aid but agreed to a trial of the IV drips after Brennan pitched it as a more sophisticated method of delivering the vitamins, minerals and electrolytes.

O'Brien said he studied training methods used by leading international trainers Aidan O'Brien and Mike De Kock as well as Waller and Darren Weir in Australia.

He agreed to the trial of IV drips post exercise on a bi-weekly basis.

O'Brien told the hearing he did not know the recipe of the drips and still doesn't.

"I have not been able to forensically analyse the drips," he told the hearing.

Brennan has been disqualified by NSW and Victorian authorities for his part in the cobalt case against Sydney trainer Sam Kavanagh and the cases against O'Brien and Kavanagh.

The vet has denied knowing the substance, vitamin complex, contained high levels of cobalt.

After visiting Aidan O'Brien in Ireland, Danny O'Brien introduced a straight 1000m grass gallop at his Barwon Heads and bought a treadmill to gallop his horses without being saddled after staying with South African De Kock.

He also spent $400,000 on high altitude boxes at his stables after learning Victoria's leading trainer Weir was using them.

The appeal resumes on October 10 with another four days set aside for evidence with final submissions in early November.