Bottles of injectable liquid sourced from the Flemington Equine Clinic are at the heart of an inquiry into high cobalt levels found in a Sam Kavanagh-trained horse.

Kavanagh, who was stood down from training last month pending the inquiry into the cobalt levels in Gosford Gold Cup winner Midsummer Sun, had been interviewed several times by Racing NSW stewards before Tuesday's hearing.

He told stewards he had paid $1000 cash for each of two bottles of a substance labelled "Vitamin Complex" which he said he had obtained from Flemington Equine Clinic.

Dr Tom Brennan, one of the co-owners of the practice, contradicted evidence taken from an employee who said she had sent the bottles to Kavanagh in Sydney by express post.

Samantha Potter said she could remember posting the bottles and recording the transaction as per normal practice.

However, the notebook in question is now missing and neither Brennan nor Aaron Corby, the manager at the clinic, could account for its whereabouts.

Potter also said she had seen Brennan draw up a drip with the contents of a similar bottle he took from the fridge in the back of his car which was parked at Danny O'Brien's Flemington stable in September or October last year.

O'Brien, Kavanagh's father Mark, Peter Moody and Lee and Shannon Hope are subjects in a Racing Victoria investigation into elevated levels of cobalt found in horses in their care.

"I never sent those bottles to Sam Kavanagh," Brennan told the hearing, adding that the cash payments were for chocolate drenches containing sugar, bicarbonate and vitamin B.

He said because Kavanagh owed the clinic $70,000 they would only accept cash.

"Did you say if Sam Kavanagh didn't play along you would wreck his father and Danny O'Brien," chief steward Ray Murrihy asked Brennan.

Brennan said Sam Kavanagh had made the story up.

Corby admitted flying to Sydney on February 17, the day after Kavanagh was told of Midsummer Sun's cobalt level.

He denied threatening Kavanagh with bankruptcy or telling him to keep Flemington Equine Clinic out of the affair.

He also denied telling Kavanagh to implicate a Queensland vet who had been known to travel to NSW selling equine products.

Brennan's partner in the clinic, Dr Ian Church, gave evidence by Skype that he could not recall details of a conversation with Dr Amy Kelly, a former Sydney-based vet with his practice.

Kelly's evidence to stewards was that she had an angry conversation with Church and told him he should tell Brennan to own up to what had happened and that her name was being tarnished.

Tim Robinson from RV's compliance and investigation unit, was present at Tuesday's hearing which was adjourned with stewards keen to interview another Flemington Equine Clinic vet, Dr Stuart Valance.