Veterinarian Dr Adam Matthews has been disqualified for 5-1/2 years over the Midsummer Sun cobalt case.

Racing NSW stewards handed down the penalty on Thursday after charging Matthews with six breaches of the Australian rules of racing.

The cumulative punishment from the six charges equated to a ban of 14-1/2 years but it was reduced due to several factors, including Matthews' previous unblemished record in the racing industry.

Stewards found Matthews was the source of two bottles of `Vitamin Complex' containing concentrated levels of cobalt which was administered to three horses trained by Sam Kavanagh, including Midsummer Sun before its Gosford Cup win in January.

Matthews formerly worked as a vet at the Flemington Equine Clinic.