Animal welfare at the Grand National is back under scrutiny after a horse died on the first day of the meeting at Aintree.
Battlefront was pulled up during the fourth race by jockey Katie Walsh and later collapsed and died.
Battlefront had cleared 10 fences in the John Smith's Fox Hunters' Steeple Chase, the first competitive test of significant course changes and new fence frames designed to improve safety.
The cause of his death has not been confirmed but it is thought Battlefront may have suffered a heart attack. A further five horses fell in the race, although none was significantly injured.
Andrew Tyler, director of Animal Aid, said: "The Aintree authorities and the British Horse Racing Authority have been claiming that major new safety measures and efficiencies would eliminate much of the risk associated with racing on the Grand National course.
"But today's Fox Hunters' Chase, in which Battlefront lost his life, was stomach-wrenchingly chaotic from start to finish. Several horses fell or were pulled up, tired and potentially injured.
"It was both utterly depressing and served as confirmation that the Aintree authorities have got it badly wrong once again."
Battlefront was the 23rd horse to die on the Grand National course since 2000, Animal Aid said.