A severe respiratory infection is likely to have contributed to the death of Randox Grand National runner Celebre d’Allen, a post-mortem has revealed.

Trained in partnership by Philip Hobbs and Johnson White, the 13-year-old was a 125/1 shot for the Aintree showpiece and was pulled up by Micheal Nolan after the final fence before then collapsing on the racecourse.

After receiving treatment, Celebre d’Allen walked into the horse ambulance and was taken to the racecourse stables for further assessment and stayed in Liverpool overnight – but although connections appeared positive regarding his recovery on Sunday, it was announced on Tuesday morning he had deteriorated overnight.

While the finding of the post-mortem is that a complication led to Celebre d’Allen’s death, rather than the exercise-associated episode itself, it is indicated the horse’s post-race condition could have been an aggravating or facilitating factor.

A statement issued by the British Horseracing Authority on Wednesday read: “The report of the post-mortem carried out on Celebre d’Allen has been shared with the trainer and owner, who have granted permission for the key findings to be published by the BHA.

Findings

“The post-mortem was carried out by Rossdales Veterinary Surgeons of Newmarket. The findings of the post-mortem state that the exercise-associated episode experienced by the horse after the race had concluded by the time of death.

“However, a severe bacterial respiratory infection (pleuropneumonia) had occurred post-race which led to the horse’s deterioration on Monday evening, with the subsequent onset of sepsis or endotoxaemia (the release of harmful substances into the bloodstream from bacteria) likely to have been a key factor in the cause of death.”

The statement continued: “Blood tests taken from the day of the race indicate that the infection had not been present in the horse on raceday, and was therefore developed after the race.

“Further bloods taken on the Monday indicated a severely compromised immune system. These indications had not been present in the bloods taken on the day of the race. This indicates that this issue emerged subsequent to the race and the exercise-associated episode.

“The heart pathology found no issues which are likely to be significant in the death of the horse.

“As stated previously, the circumstances around the fatality – as is the case with any fatal injury – are being reviewed in detail. The post-mortem forms one part of this process. In addition, the Grand National is always reviewed in detail after every running of the race by the BHA and the Jockey Club.”

The raceday stewards suspended Nolan for 10 days (April 19-26 and May 3 and 5) after concluding he “had continued in the race when the horse appeared to have no more to give and was clearly losing ground after the second-last fence”.