The driver of Racing Victoria's cobalt rule believed there was no issue over the testing despite the racing labs lacking specific accreditation covering horse urine.

Testing of urine was straightforward whether it was from a person or a horse, Racing Victoria head vet Dr Brian Stewart said.

Trainers Danny O'Brien and Mark Kavanagh, as well as Lee and Shannon Hope, are trying to overturn their cobalt disqualifications in part by arguing the labs involved were not properly accredited to do the testing at the time.

No laboratory in the world had an accredited method to test for cobalt in equine urine when Racing Victoria introduced its cobalt threshold in April 2014, the appeal has heard.

Stewart said while it was better in principle to have a method specific to a species, an official racing laboratory's scope of accreditation was adequate if it covered urine generally.

"I was satisfied that the testing in human urine or equine urine was equivalent," Stewart told the Victorian Civil and Administrative Tribunal on Wednesday.

"It's a straightforward, simple analytical procedure.

"Human urine was in the scope of the laboratory and I was satisfied that was acceptable."

Stewart said the advice from Victorian lab Racing Analytical Services Ltd was that human accreditation was acceptable.

He said testing for cobalt in plasma was a different issue as there was some controversy about the appropriate method.

Racing Victoria chief steward Terry Bailey on Wednesday blamed a backlog at Perth lab ChemCentre for the delays in telling O'Brien and Kavanagh about their cobalt positives.

The two trainers learned of the results on January 14, 2015 - Kavanagh for a horse that raced on October 4, 2014, and O'Brien for three horses in November races.

O'Brien later learned of a fourth positive from a December race.

O'Brien argues he would have stopped using drips containing a substance called vitamin complex if he had known about Kavanagh's October positive.

He told stewards: "We have a situation where there was horse that raced on the first Saturday of October that went over on these drips and you guys left the meter running until the middle of January."

Bailey said Racing Victoria wanted a timely testing process but there was a backlog at Perth-based ChemCentre, which was "engulfed" with samples from racing regulators across Australia.

"We were in the hands of ChemCentre," he said.

Bailey did not believe the delay was caused by RASL's decision to split samples from mid-2014, with ChemCentre testing for cobalt and the Victorian lab for everything else.

"My understanding was it was the backlog at ChemCentre, not the splitting process," he said.

Stewart, who leaves Racing Victoria in November, will continue his evidence on Thursday.