Victorian trainer Mark Kavanagh has denied paying a vet $3000 for the substance called vitamin complex at the centre of his cobalt case.
Dr Tom Brennan maintains Kavanagh and fellow Flemington trainer Danny O'Brien knew he was adding the substance to drips given to horses in their stables and they each paid $3000 for three bottles of it.
Kavanagh told his appeal against his three-year cobalt disqualification that he did not pay Brennan $3000 cash and there was never any discussion about it costing $1000 a bottle.
Kavanagh said Brennan never showed him the vitamin complex bottle and if he had done so, "they wouldn't have been using it on my horses".
Kavanagh has since seen a photo of the bottle, which he said did not even look like a professionally-made product.
Brennan did not tell stewards about the vitamin complex until July last year, six months after O'Brien and Kavanagh learned about their cobalt positives.
Questioned at the time about Brennan's claims, Kavanagh told stewards he had nothing to do with "that stuff" and only authorised the use of legitimate vitamins in drips.
Kavanagh on Friday said he trialled an IV drip regime for delivering vitamins on Brennan's suggestion but stopped it after a month as as the horses were not going any better.
Kavanagh said seven days after he learned of his cobalt positive, Racing Victoria's calendar contained a warning about not using large doses of vitamins including registered products such as VAM.
That was despite its chief vet having attended conferences where that was discussed, he said.
"At the time I was under the impression that they disregarded and ignored the warnings towards the trainers," Kavanagh told the Victorian Civil and Administrative Tribunal.
"It's my personal opinion now they hid them."
Racing Victoria brought in a cobalt threshold in April 2014, ahead of the national rule in January 2015.
A bottle of vitamin complex Brennan sent to Kavanagh's son, Sydney trainer Sam Kavanagh, was found to contain high concentrations of cobalt.
Mark Kavanagh, who had one horse return a cobalt positive, will continue giving evidence on Monday, the 22nd day of the appeal.