A senior racing official has denied pressuring Sam Kavanagh to change his evidence to stewards to protect a friend the trainer named as his supplier of cobalt.

Sam Kavanagh is at the centre of an inquiry sparked by elevated levels of cobalt and the presence of caffeine found in Midsummer Sun after he won the Gosford Cup in January.

Matt Rudolph, ATC executive manager - racing, has been asked to show cause why he should not be penalised for his part in a meeting on March 2 with Kavanagh and his father, Melbourne trainer Mark Kavanagh, at a Sydney hotel.

At a hearing before a sub-committee of the Racing NSW board on Tuesday, Rudolph said he agreed to a request from Mark Kavanagh to talk to his son over lunch.

A few days earlier, Sam Kavanagh had told stewards the bottles found in his stable identified to have high levels of cobalt had come from his vet, Dr Tom Brennan of the Flemington Equine Clinic.

Rudolph told Tuesday's hearing he and Brennan were long-time friends and he did not believe at the time the vet could be the supplier and agreed to a request from Mark Kavanagh to talk to his son who he believed was in a distressed state.

Sam Kavanagh told the hearing he felt he had been ambushed.

"Matt Rudolph told me to `take Tom out of this'," Kavanagh told the hearing.

"I felt ambushed."

Kavanagh said he felt suicidal and told his father: "I may as well throw myself off a 20-storey building".

Mark Kavanagh described Rudolph's attitude to his son as "quite openly savage".

Rudolph said he believed Brennan was innocent and he told Sam Kavanagh: "The Tom Brennan I know would not supply cobalt."

"I was only declaring an opinion. I wasn't holding a gun to his head," Rudolph said.

"I told him if he lied he would get found out. I thought he had lied."

A forensic examination of his phone revealed Rudolph had deleted messages between himself and Brennan before February.

Peter Braham, counsel assisting Racing NSW, put it to Rudolph he went to the meeting on behalf of Brennan and not as part of his official role dealing with trainers.

"He (Brennan) was the puppet master and you were the puppet," Braham said.

Mark Kavanagh is one of five Victorian trainers charged with cobalt offences and until late last year, Brennan was also his vet.

Brennan has been charged by Racing NSW stewards for supplying Sam Kavanagh with "Vitamin Complex" a substance later found to contain a large amount of cobalt.

He has been charged in Victoria in relation to the cobalt charges against Mark Kavanagh and fellow Flemington trainer Danny O'Brien.

Brennan has also admitted to lying to Racing NSW stewards when first questioned about his involvement.

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