Trainer Mark Kavanagh has told an inquiry he felt bullied by Racing Victoria stewards investigating a high cobalt level in one of his horses.

"It felt like they were trying to beat a confession out of me," Kavanagh said.

Kavanagh, fellow trainer Danny O'Brien and vet Tom Brennan appeared for the sixth day of the Racing Appeals and Disciplinary Board's hearing into charges of elevated cobalt on Monday.

Kavanagh said he had been interviewed by stewards on three occasions after January 14, the day he learned of Magicool's elevated cobalt reading.

He said his story did not change during further interviews on May 13 and July 21.

He also called Brennan a liar. He said the vet's evidence he couldn't vouch for Vitamin Complex and that it would cost anywhere between $10,000 and $100,000 to have the product tested was false.

Kavanagh said there no discussions, nor did he pay Brennan $3000 cash. He said he trusted Brennan and allowed the vet to begin the alternative regime, replacing the previous practice of oral vitamins and saline drenches with an intravenous drip.

Brennan has admitted adding Vitamin Complex to the drip but denied knowing it contained high levels of cobalt.

Racing Victoria's counsel Jeff Gleeson accused Kavanagh of deliberately not telling stewards of a second mobile phone he bought to communicate with his son, disqualified NSW trainer Sam Kavanagh.

Kavanagh said stewards told him all phone records requested were up to January 14, the date he was informed of the elevated reading and said he would now provide RV investigators with his second phone.

Earlier O'Brien rejected claims he lied to stewards after being made aware in January of elevated cobalt levels in four of his horses.

O'Brien said he had not changed his story despite Gleeson asserting he had done so on several occasions between January and July.

"I'm really offended by the word lie, Jeff," O'Brien said.

O'Brien has maintained throughout the hearing he did not know the recipe of the drips given to his horses by Brennan.

He also said he didn't know Vitamin Complex contained high levels of cobalt until July 21 when Brennan after Brennan had been interviewed by stewards.

O'Brien has had a strained relationship with stewards since January 2013 when they conducted a trial program into TCO2 levels.

Two of O'Brien's horses were detained after a race meeting, a matter which became public.

Stewards later apologised for the incident.

The two trainers also questioned how Peter Moody, who also faces cobalt charges, knew of Kavanagh and O'Brien's high readings before they did.

The hearing has been adjourned until Friday for submissions.