Tragic comeback for 2007 National runner-up

The return of McKelvey to the Grand National a year after vets advised he might never race again was supposed to be one of those stories of equine triumph over adversity for which the steeplechase is known. Instead, the horse – unable to stand after throwing his jockey then colliding with a railing – had to be put down.

While the trainer of McKelvey – which came within less than a length of winning jump racing's most glittering prize a year ago – declared himself "absolutely devastated", others debated whether the thoroughbred should have been entered in Saturday's £300m race at all.

Animal rights campaigners suggested McKelvey – whose recovery from a ruptured tendon sustained in the final moments of the 2007 Grand National had been chronicled by a BBC film crew – was not suited to the gruelling 4.5 mile course after racing just twice so far this season.

But racing sources emphasised the care and attention lavished on the horse by its trainer, Peter Bowen, and revealed that the injury which led to the eight-year-old being destroyed was "completely unconnected" with last year's tendon injury.

McKelvey, an outsider with odds of 28-1 despite coming a close second to Silver Birch in 2007, unseated Tom O'Brien at the 20th fence and was hurt while running loose. He was the 51st horse to have died at the Aintree meeting since 1991. In the past 12 months, 174 horses have died in British races.

The British Horseracing Authority (BHA), which is responsible for the welfare of horses on tracks, said the injury rate at the Grand National was now 0.6 per cent – in line with the rate for all jumping races – after measures such as changes to the fences and an irrigation system were introduced to improve safety on the course.

A BHA spokesman said: "What happened to McKelvey was terribly sad. But it was nothing to do with the injury he sustained last year. The horse was assessed prior to being allowed to race. After unseating his rider, he ran loose and collided with one of the railings. We are waiting for the results of a post mortem examination but it seems the horse was put down as the result of an injury to its back."

For Mr Bowen and the staff at his stables near Haverfordwest, Pembrokeshire, west Wales, it was all supposed to have been very different after a year of setbacks. Moments after losing by three quarters of a length to Silver Birch in 2007 – narrowly missing the feat of becoming the first Welsh horse to win the Grand National in more than a century – it was found he was lame from a severe leg injury.

Casting aside advice from vets that the injury meant the horse might not run again, Mr Bowen spent three nights sleeping in McKelvey's stable to nurse him through the worst moments before embarking on a long programme of rehabilitation, including daily visits to a specially-designed swimming pool.

The recovery was watched by millions of television viewers after the BBC's The One Show asked to film the process. A "stable cam" was installed so fans could log on and watch his progress.

Prior to the Grand National, Mr Bowen, who has also seen his horses struck by a winter virus and three of his stable failing doping tests due to a worming medicine wrongly prescribed by vets, said he was happy that McKelvey had made a full recovery. He was entered in just two races this season and performed poorly, but his owners said this was no indication of his potential for Saturday's meeting.

Mr Bowen said: "He's fine. No problems. It was a bit of a blow at the time and it was a slow job, but that's over now."

The atmosphere at the stable yesterday was predictably sombre. Mr Bowen, the son of a greengrocer who has built up his yard from scratch with his wife Karen and saw his horses win £1m last year, said in a statement: "We are obviously absolutely devastated at the loss of McKelvey at the Grand National. We go through everything, no stone is left unturned. The most important thing to us is that the horses are happy in their work and are healthy."

Supporters of Mr Bowen dismissed any suggestion that McKelvey should not have run. One member of his yard said: "McKelvey was our baby and his health and welfare were paramount. He will be truly missed."