Punters have vowed never to bet on horse racing again after seeing an animal in convulsions as he died after falling on his neck in the Grand National.

Up For Review was the first horse to be killed at the prestigious race since 2012, and one of three fatalities in the final 48 hours of the three-day event.

About 70,000 spectators at Aintree and millions more television viewers saw the horse land on his neck at the first fence, before appearing to thrash about in pain.

Officials erected screens to block the carcass from race-goers and television cameras.

Horseracing chiefs siad they will review safety of the 30-jump course. But the race came in for a torrent of criticism for its “barbarity”, with some pledging to boycott it in future.

Animals in entertainment Show all 20 1 /20 Animals in entertainment Animals in entertainment Dogs perform tricks at a circus in France Jo-Anne McArthur/One Voice Animals in entertainment Dolphins perform at an aquarium in France Jo-Anne McArthur/One Voice Animals in entertainment Kiska, a lone orca, in the tank at Marineland in Canada Jo-Anne McArthur/We Animals Animals in entertainment A dolphin performs tricks for tourists at the Kahala Hotel in Hawaii Jo-Anne McArthur/We Animals Animals in entertainment A bull lays dying as a matador prepares to deliver the fatal blow to its spine Jo-Anne McArthur/We Animals Animals in entertainment Zeus, a walrus at Marinepark in Canada, performs for spectators Jo-Anne McArthur/We Animals Animals in entertainment Penguin enclosure at SeaWorld in San Diego, California Jo-Anne McArthur/We Animals Animals in entertainment A competitor is thrown off a bull during a rodeo event in Montreal, Canada Jo-Anne McArthur/Montreal SPCA Animals in entertainment Saw fish in an aquarium Jo-Anne McArthur/We Animals Animals in entertainment A picador stabs at a bull Jo-Anne McArthur/We Animals Animals in entertainment Orcas perform at SeaWorld in San Diego, California Jo-Anne McArthur/We Animals Animals in entertainment Visitors feed fish to sea lions at Marineland in Canada Jo-Anne McArthur/We Animals Animals in entertainment A frog tank in an aquarium Jo-Anne McArthur/We Animals Animals in entertainment A sea lion performs at SeaWorld in San Diego, California Jo-Anne McArthur/We Animals Animals in entertainment A competitor rides a bull during a rodeo event in Montreal, Canada Jo-Anne McArthur/Montreal SPCA Animals in entertainment The Beluga whale tanks at Marineland in Canada Jo-Anne McArthur/We Animals Animals in entertainment The Beluga whale tanks at Marineland in Canada Jo-Anne McArthur/We Animals Animals in entertainment Gift shop trinkets at the Kahala Hotel in Hawaii Jo-Anne McArthur/We Animals Animals in entertainment A young boy reaches out to touch a dolphin as it swims by at the Kahala Hotel in Hawaii Jo-Anne McArthur/We Animals Animals in entertainment Turtles at an aquarium in Havana, Cuba Jo-Anne McArthur/We Animals

Anthony JD tweeted: “To watch #upforreview suffering so badly live on TV has seriously affected me. I knew as soon as it happened it was bad. Never betting on horse racing ever again and I don’t want to watch another race as long as I live. Poor horse. Looked a beauty who didn’t deserve that.”

Others agreed, saying they felt sick at the “horrific” death and would not bet on the Grand National again.

The “You bet they die”(#Youbettheydie) hashtag was widely used, and many also signed a petition calling for ITV to stop broadcasting the race.

British Horseracing Authority bosses insisted Up For Review felt no pain and died instantly.

The “thrashing” seen was probably convulsions after death, a spokesman said, adding that a post-mortem examination would find the cause of death.

“We will never remove the level of risk to zero, and the same applies to all activity involving horses. However, the level of risk now sits at 0.2 per cent,” said David Sykes, head of equine health and welfare.

The initial pain would have been great Dene Stansall

But Dene Stansall, a former racing fan, now racing consultant for Animal Aid, said it was the worst Grand National death he had seen.

“Up For Review’s death wouldn’t have been instant – it would have taken a few seconds, maybe up to two minutes,” he said. “The initial pain would have been great.

“You can’t say categorically the spinal column would have broken cleanly. The heart could still be beating and legs twitching after the neck has snapped.”

The 40 runners was far too many, Mr Stansall said.

He said he has seen hundreds of horses suffer broken necks, and some horses left quadriplegic on courses – alive but unable to move their limbs.

Forest des Aigles and Crucial Role were put down after being injured in different races during Ladies Day at Aintree.

We worked in the run-up to this year’s meeting to ensure preparations to keep it safe were the best ever British Horseracing Authority

In all, 84 horses have died at the Grand National since it began in 1839.

Labour MP Chris Williamson tweeted: “It’s clear that Aintree racecourse is still far too dangerous and inflicts needless cruelty on the horses.”

Ricky Gervais’s comment “Why would you gamble with a horse’s life for fun?” had more than 31,000 likes.

But defenders said racehorses were loved and “treated like royalty”.

The BHA said if evidence showed further improvements could be made, they may be.

After a major review last year a raft of changes, including increasing pre-race examinations, were introduced.

The spokesman added: “Aintree racecourse and the BHA worked together in the run-up to this year’s meeting to ensure preparations to keep the event safe were the best ever.

“However, there’s a level of risk involved in any activity in which horses take part. We work hard as a sport to keep those risks to a minimum and remove avoidable risk. We will take a measured, evidence-based approach to assessing the incidents, which will include reviewing video footage of all incidents and working with jockeys and trainers.”

BHA figures show about 200 horses die on racecourses every year.