Veterinary surgeon Adam Matthews has been found not guilty of being the supplier of cobalt in the long-running Midsummer Sun affair.

The Racing NSW Appeal Panel said although both Flemington Equine Centre partner Dr Tom Brennan and trainer Sam Kavanagh named Matthews as the source of Vitamin Complex, it could not be satisfied that was the case.

Matthews was however found guilty of being a party to the administration of a raceday drench given to the Kavanagh-trained Midsummer Sun who tested above the legal limit for cobalt when he won the Gosford Cup on January 9 last year.

The result sparked an investigation into other horses in the Kavanagh stable which were given the Vitamin Complex, later found to contain high levels of cobalt.

The raceday administration charge carries a mandatory six-month ban.

Kavanagh and Brennan both received lengthy disqualifications with the panel sustaining most of the stewards' charges against the pair.

They did, however, clear Brennan of threatening Kavanagh if he named the Flemington clinic as the source of the drips.

Kavanagh was found not guilty of a charge relating to giving Xenon gas to a horse in his stable and of giving a raceday drench to Centre Pivot on January 24, 2015.

The panel will hear oral submissions on penalty on May 19.

Cobalt is a naturally occurring trace element in horses at low levels and is present in Vitamin B12.

It is toxic at high levels with the Australian threshold set at 200mcg per litre of urine.