Queensland jockey Luke Tarrant has been disqualified for six months after admitting to head-butting fellow rider Larry Cassidy at the weighing scales at Doomben.

As well as the seriousness of the physical incident, stewards took into account the breach of the COVID-19 social protocols and the potential for Tarrant's actions to have an adverse effect on the racing industry.

It is the latest disqualification or suspension for Tarrant who had been making a success of a comeback after facing criminal drugs charges.

Tarrant and Cassidy had been involved in a scrimmage during the ninth race on Wednesday.

Tarrant pleaded guilty to misconduct which started out as a verbal altercation with Cassidy in the vicinity of the scales area.

When Tarrant head-butted his fellow jockey, his helmet made contact with Cassidy's nose causing an injury.

Tarrant was disqualified for six months to commence immediately and to expire on October 22.

Stewards said in considering penalty they took into account the significant contact to Cassidy.