The veterinarian who admitted selling cobalt to two thoroughbred trainers was an "admitted liar" whose evidence was questionable, a Racing Victoria hearing has been told. High-profile trainers Mark Kavanagh and Danny O'Brien appeared before a panel of stewards on Wednesday afternoon, forced to make a case for why they should not be stood down while they await trial on doping charges. If stood down, the pair would miss the lucrative Melbourne spring racing carnival – a move that would end both their careers, they said. If it was deemed they posed an unacceptable risk to the integrity or reputation of racing, they would be sidelined until their entire case was heard. The trainers' representative Damien Shields said Tom Brennan, a veterinary surgeon who recently said he had sold vitamins to the pair that contained the banned substance cobalt, could not be trusted. Shields repeatedly tried to cast doubt over Brennan's credibility, calling him an "admitted liar." But Jeff Gleeson QC, assisting Racing Victoria, said the chances of the high levels of cobalt detected in one of the horses involved occurring naturally was less than one in 7 million. O'Brien and Kavanagh had been on radio criticising stewards in relation to the matter, so Shield's claims that they had maintained a dignified silence throughout were questionable, he said. Shields said there was no doubt the cobalt had entered the horses' systems via drips, but that there was no proof that Kavanagh and O'Brien had known, or should have known, the substance was in them. He said Brennan had admitted to breaching his fundamental duties as a vet and questioned if he could be trusted to tell the truth. Shields also argued there was no evidence that cobalt was performance enhancing, despite the public perception that is was "rocket fuel" and damaging to horses. "The science of cobalt is still evolving, it's not settled, we say, in any way," he said. Shields said there was no risk of his clients using cobalt in the future. Earlier, trainer Peter Moody told Racing Victoria stewards that he could not afford to have his prizemoney percentages frozen until the result of his cobalt case later in the year. Terry Bailey asked Moody through his legal counsel if he would accept a proposition of having his prizemoney percentages frozen in the form of a condition of the standing notice. Legal counsel for Moody, one of Australia's most successful horse trainers, said that Moody could not accept the freezing of his prizemoney percentages. However, earlier in the day the Hope training partnership - Lee and Shannon - told stewards they would be prepared to accept having their prizemoney percentages frozen. They said it was important they maintain training and would have no concerns with the money being frozen until the result of the cases. Rob Stitt QC, for the training partnership, said they had 30 horses in work at their stables in Kilmore and Seymour. Matt Stirling, for Peter Moody, told stewards that Moody trained 110 horses at his Caulfield stables and he employed 70 people and had a payroll of $50,000 a week. And those people's jobs would be terminated and Moody would face a termination payment of $200,000. He would have to contact the owners of 110 horses to tell them their trainer of choice could not continue. "And it is a $15 million business and Moody owns several horses in his own stable and the freezing of his percentages would not work," Stirling said. Moody said after his hearing that "every dollar the business earns is re-funnelled back into the business". Moody said he would continue as he has throughout, to work with stewards over being charged after Lidari returned a positive swab for cobalt. Bailey told they Hopes and Moody that they would be advised of the result of Wednesday's hearing shortly.