A racehorse is being treated for a suspected fractured pelvis as a result of the Melbourne Cup amid calls to boycott the event due to concerns around animal cruelty.
Rostropovich, who finished last of the 24 horses in the prestigious $8 million race on Tuesday, was reportedly taken to Werribee Vet Clinic following the event.
Rostropovich finished more than 30 lengths behind the second-last placed Mustajeer after being pulled up by Dwayne Dunn.
Witnesses at the track said the horse was unable to put weight on one of its legs, the Coalition for the Protection of Racehorses said.
Six racehorses have died as a result of injuries sustained during the Melbourne Cup since 2013.
One of Rostropovich's trainers, David Hayes, said the horse was unable to "weight bear".
"But with a lot of painkillers, he's relieved. It's a sad story anyway," he said.
Racing Victoria released a statement confirming Rostropovich was inspected by veterinarians at the tracks and found to be "lame", which means unable to walk properly, and transported to the University of Melbourne Equine Centre for further assessment.
"Rostropovich will be confined to box rest for the near future and will be closely monitored over the coming days by veterinary staff," Racing Victoria said.
PETA spokesperson Emily Rice said Rostropovich was the latest horse to have been injured or killed during the "disgrace that stops the nation".
"We seriously hope that Rostropovich doesn't become another Red Cadeaux - kept alive until the carnival hype dies down and then euthanised," said Elio Celotto, Campaign Director for the Coalition for the Protection of Racehorses.
Rostropovich was having his second run in the Melbourne Cup.
He finished fifth in last year's race when trained by Aidan O'Brien and ran this year for the Lindsay Park partnership of David and Ben Hayes and Tom Daberni.
Party, 'without engaging in animal abuse'
A small contingent of anti-horse racing protesters, many wearing dresses, suits and hats similar to those attending the races, gathered at Flemington Racecourse on Tuesday to call for an end to the controversial sport.
"Cup day is a very socially ingrained day where people have parties. We did a protest on the course the other day but on Cup Day it's important to offer an alternative event for people," Coalition for the Protection of Racehorses spokeswoman Kristin Leigh said.
"It is a public holiday and everyone gathers, they might not want to protest but they want to party, so we wanted to show that it's possible to do that without engaging in animal abuse".
Vow And Declare's part-owner, former NSW politician Geoff Corrigan, acknowledged the recent allegations of animal cruelty involving ex-racehorses that led to Tuesday's protests.
"There's a social contract involved with racing," Mr Corrigan said.
"That social contract's been fractured a little bit in the past two weeks."
But Mr Corrigan said he was very pleased with the efforts that have been made by Racing Victoria, Racing NSW and Racing Queensland to address anti-cruelty concerns.
Attendance continues decline
The number of people attending the Melbourne Cup has dipped again, for the fourth year in a row.
There were 81,408 racegoers at Flemington Racecourse on Tuesday to watch the Australian-bred, trained, ridden and owned Vow And Declare win the Cup.
That was down slightly from last year's rain-affected number of 83,471, with both years marking the lowest attendance since 1995.
Winning trainer Danny O'Brien said he does not believe the Melbourne Cup carnival has lost its gloss.
"I've been all around the world to English derbies to Royal Ascot to the Kentucky Derby, but nothing comes close to this," he said.
"You have a whole city that stops, the rest of the country does as well."
Crowd numbers at the Melbourne Cup have been falling in recent years - last surpassing 100,000 in 2015.
