The welfare of jump horses will again come under scrutiny after Little Josh became the second fatality at Aintree in as many days.
The Nigel Twiston-Davies-trained gelding was put down after breaking his shoulder in the John Smith's Topham Chase.
Little Josh parted company with rider Sam Twiston-Davies in the extended two-mile-five-furlong event, run over the Grand National course.
A tweet from Aintree racecourse read: "We can sadly confirm that Little Josh broke a shoulder in the Topham Chase. He was treated immediately but needed to be humanely put down."
The news follows the the collapse and death of Katie Walsh's mount Battlefront after being pulled up in the John Smith’s Fox Hunters’ Chase.
The tragedies represent an excruciating start to the meeting for Aintree officials, who have responded to fatalities in each of the last two Nationals with a series of modifications to the controversial course.
Speaking after today's incident Professor Chris Proudman, veterinary advisor to Aintree, said: "We are sad to confirm that is has been necessary to humanely put down Little Josh on welfare grounds, as a result of his fall at the 15th fence in the John Smith's Topham Chase.
"He received immediate veterinary attention for a broken shoulder, but this injury was not treatable and it was the necessary course of action."
All 28 other horses in the race returned safely.
John Baker, Aintree and North West Regional Director for Jockey Club Racecourses, said: "I would like to extend our sympathies to the connections of Little Josh following his fall in the John Smith's Topham Chase.
"We have made significant improvements in safety at the course, but we also recognise that jump racing carries risk you can never completely remove from the sport."
Aintree said jockey Liam Treadwell received medical assessment on course and was taken to hospital for further assessment. Andrew Lynch was being assessed in the medical centre on course.
Grand National-winning trainer Twiston-Davies paid tribute to Little Josh, and did not attribute blame to the much-scrutinised fences.
He said: "He's gone out doing what he loved the most, he's jumped round those fences before and it's one of those things.
"It could happen anywhere, it could happen at home and it's not the fences - it could have happened at a park course.
"It's desperate, as he is one of Sam's favourite horses and he has been a great servant."
Tomorrow the Grand National takes place. More flexible cores have been installed in the fences, and the ground has also been levelled off at several jumps. In an effort to curb the early pace, meanwhile, the National start has been moved 90 yards closer to the first fence. But calls to reduce the field size have been rejected. “We want to maintain the character, tradition and history of the National,” Baker stressed. “To have 40 runners is unique to the race and important to us. The track is wide enough to cope with that number.”
All those at Aintree will be desperate the fatalities do not extend to three in three.