A fiery outburst by trainer Danny O'Brien has put an end to the fifth day of a hearing into cobalt charges against him.

O'Brien had a heated exchange with Racing Victoria's counsel, Jeff Gleeson, QC, over the way he was unable to answer his questions at the inquiry before the Racing Appeals and Disciplinary Board in Melbourne on Friday.

"I'm so pissed off by you twisting things around," O'Brien said to Gleeson which prompted Judge Russell Lewis to call an end to the day's proceedings.

O'Brien had been asked whether on January 14, the day he was notified of elevated cobalt readings to Bondeiger, Caravan Rolls On and De Little Engine, stewards had asked him if anything had changed in his stable.

The trainer replied no, but wanted to add the stable was using pre and post-race drips.

Earlier O'Brien's lawyer Damian Sheales took O'Brien through the horses in the stable that had been receiving drips.

Gleeson wanted to know the importance and if they were going to go through all horses as it was taking time to which O'Brien said: "Jeff, I'll be spending three years out".

Vet Tom Brennan, O'Brien and Mark Kavanagh are before the RAD Board over four O'Brien and one Kavanagh-trained horse returning cobalt levels above the 200mcg per litre of urine threshold.

O'Brien told the hearing he heard a well-known trainer had been having considerable success with post-race IV drips.

He then discussed with Brennan the prospects of using IV drips post-workouts that would quickly replenish electrolytes, vitamins and minerals on a trial basis.

He said he had not set a time frame or number of runners for the data to be finalised.

O'Brien said the concept was that it would aid recovery and benefit horses that may race through to the back-end of the spring.

He said the only justification for the trial was he couldn't allow the owners to pay too much until it was finished.

The trainer said he paid Brennan $3000 from his personal account to cover expenses of the trial.

Brennan has said he added a substance called Vitamin Complex to the drips but that neither he nor the trainers knew it contained high levels of cobalt.

O'Brien had an unblemished career with no positive tests for prohibited substances until he was notified of his cobalt results.

He was in a state of shock and knew little of cobalt and had two conversations, one with Brennan over concerns there were horses from South Australia using the substance and winning races in Victoria and another with chief steward Terry Bailey when the cobalt threshold came into force in April 2014.

O'Brien said if he was disqualified it would finish him in the industry and force him to sell his Barwon Heads property.

The hearing continues on Monday with O'Brien to be cross examined and Kavanagh expected to give his evidence.