Counsel for vet Adam Matthews has successfully applied to have the stewards panel changed in his hearing relating to the Sam Kavanagh cobalt case.

The original panel which deliberated in the Kavanagh inquiry sparked by high levels of cobalt in Midsummer Sun determined penalties against several parties.

Matthews' solicitors applied to have that panel - Ray Murrihy, Keith Mason QC, Marc Van Gestel and Chris Polglase - excused on the basis they had already heard and determined charges against Kavanagh, Dr Tom Brennan and others.

Racing NSW chief executive Peter V'landys said those stewards acceded to the request and he appointed a new panel.

The hearing began on Tuesday in front of Jim Walshe, Ray Livingstone and Thomas Moxon.

Chief steward Ray Murrihy appeared before the panel as prosecuting steward.

Kavanagh named Brennan as his supplier of Vitamin Complex, a substance with a high concentration of cobalt, with Brennan in turn naming Matthews as his source.

Matthews has been charged with six offences including supply of the prohibited substance and improper conduct in doing so.

Brennan, who has also been charged by Victorian authorities, has stood down from treating racehorses at the Flemington Equine Clinic where Matthews previously worked.

Kavanagh and Brennan have both appealed disqualifications arising from the case.