A vet who denies being involved in supplying cobalt has to give evidence to Victorian trainers Danny O'Brien and Mark Kavanagh's appeals against their disqualifications.

Dr Adam Matthews' barrister Glenn Casement on Monday tried to have a summons for the vet to appear as a witness set aside on medical grounds, but was unsuccessful.

The Victorian Civil and Administrative Tribunal has previously heard Matthews is suffering from a significant psychiatric disorder that requires ongoing treatment in hospital.

The court was closed to the public while the psychiatrist who is treating Matthews gave evidence on Monday.

Matthews has been summonsed to appear before VCAT on Wednesday.

Matthews denies fellow vet Dr Tom Brennan's claim he supplied bottles containing a substance called vitamin complex that Brennan gave to horses in the O'Brien and Kavanagh stables.

The Racing NSW Appeal Panel found Matthews not guilty of being the supplier of cobalt in a bottle of vitamin complex Brennan sent to Kavanagh's son, Sydney trainer Sam Kavanagh.

Matthews will be the last witness in Racing Victoria's case against Kavanagh and O'Brien.

The trainers will then both give evidence.

O'Brien was in January disqualified for four years and Kavanagh for three years, while Brennan received a five-year ban and has also been outed by NSW stewards.

Father-and-son training partners Lee and Shannon Hope are also appealing their respective three and five-year cobalt disqualifications.

The Hopes, Kavanagh and O'Brien are trying to have their bans overturned in part by arguing the laboratories that did the cobalt testing were not properly accredited at the time.

The Hopes' appeal has been set down for six days in October and November, including during Melbourne Cup week.