Father and daughter training partners Terry and Karina O'Sullivan have been disqualified until the start of 2020 after being found guilty on three cobalt related charges.

The Racing Appeals and Disciplinary Board on Thursday disqualified the pair until December 31, 2019 after two horses returned excessive cobalt readings.

Darragh, on two occasions, and Gold A Plenty returned levels above the then threshold of 200 micrograms per litre in urine in pre-race samples in 2015 and 2016.

The threshold is now 100mcg/L.

The O'Sullivans faced nine charges laid by Racing Victoria stewards and were found guilty of three.

They had the most serious charges dismissed by the RAD Board of administering, or causing to be administered, a prohibited substance, being cobalt, for the purpose of affecting the performance or behaviour of a horse in a race.

The pair were found guilty of the lesser charge of administering or causing to be administered a prohibited substance.

The O'Sullivans will consider their options for appeal.