The deaths cast a pall over the annual celebration and reignited a bitter debate in Australia about the ethical treatment of racehorses, with fresh calls for a ban on whipping and a claim that one horse is dying nearly every three days.
The claim by Australia's Coalition for the Protection of Racehorses is, however, at odds with figures released yesterday by New Zealand Thoroughbred Racing, which showed four out of 30,031 horses starting in races this year died from injury.
The "sudden death syndrome" suspected to have felled Admire Rakti is thought to occur in about 0.007 per cent of racehorses.
Professor Chris Riley, who specialises in equine clinical research at Massey University, expected everything would have been done to save the Japanese stayer and Araldo on the day.
"When a horse breaks its leg at the track, often these injuries happen at high speed - in this case it was a high-speed kick - and once the bone is open and infected, and the vessel is damaged, the chance of saving the leg is pretty low," he said.
"For example, in a fracture of the humerus - that's the thigh bone of a horse - success rates are only around 10 per cent, and they are usually very young horses, not full-grown athletic horses."
Professor Riley expected the decision to put down Araldo would been made by expert vets and saved the animal from a painful death.
"If the assessment wasn't going to achieve a good outcome, then I'd respect that decision - they are very experienced people, and in the end, they want the best for the horse and the owner, and the public is the last in that chain."
He considered the death of Admire Rakti - who with 800 metres left to run in the Melbourne Cup stopped responding to the whip of jockey Zac Purton - was a "freak accident".
Dr Brian Stewart of Racing Victoria believed an irregular heartbeat had progressed to a condition called ventricular fibrillation - which means the heart beats in a bad rhythm - and resulted in an effect similar to a heart attack.
Professor Riley believed that whatever the cause, it was something "substantially internal" which the stress of racing might have pushed over the edge.
The deaths were shocking for everybody involved, he said, but the public needed to understand racing was at some level a natural activity for the horses.
"Their athleticism is a natural expression of what they are as a creature."
Dr Barry Drayton, president of the New Zealand Equine Veterinary Association, also considered the deaths an extremely rare occurrence that just happened to take place at the biggest event on Australia's racing calendar.
