Regal Heights and Minella Four Star collapsed at the end of the four mile Scottish Grand National at Ayr racecourse.
Regal Heights died of a suspected heart attack, while Minella Four Star is thought to have died of internal bleeding.
Their deaths come in the wake of last Saturday’s Grand National – the highest profile event in the racing calendar – where two horses died after falling at fences.
The races are two of the longest in the racing calendar.
Saturday’s horses are among 60 to have died in races so far this year – equivalent to just over four a week.
Animal charities have called for better regulation of the sport.
Rest in peace, Regal Heights and Minella Four Star.