Racing Victoria has announced amendments to its coronavirus protocols that keeps different riding groups separated.
RV has separate groups for jockeys that ride in jumps and highweight races.
With the Casterton and Coleraine race clubs unable to appropriately segregate jumps and Flat jockeys, RV has decided to make programming changes.
The Casterton Cup meeting on May 17 will become an all-Flat fixture.
The meeting at Casterton on June 27 now becomes a day for jumps riders only with a fourth jumps race added and the three Flat races converted to highweight races.
Meetings at Casterton and Coleraine on August 9 and 16 respectively will be a mixture of jumps and highweight races.
RV's executive general manager of racing Greg Carpenter said the industry biosecurity protocols are as important now as they were six weeks ago.