Another horse died at Aintree yesterday. The number of deaths in racing in the past year is now 180

Horse racing authorities refuse to make public the details of which horses die on which courses, but The Independent on Sunday can reveal that there have been around 180 deaths in the past year.

Tyneandthyneagain died during the Grand National yesterday after unseating its jockey. The horse suffered a fatal fall at the 11th fence. It was the second casualty of this year's meeting at Aintree, the first having been Terivic, which fell and broke its back on Friday at the notorious Bechers Brook fence. The shocking death toll at the Cheltenham Festival in March, when nine horses were killed, had already made it a sad year for racing.

Among the record numbers of punters at Aintree this year were protesters from the Animal Aid campaign group, who say 375 horses are "raced to death" each year. Of these they claim that 110 deaths occur on race courses. But that is less than the figure revealed to this newspaper by Peter Webbon, chief executive of the new Horseracing Regulatory Authority (HRA), which took over the running of the sport last week. "For every 1,000 horses that went down to the starting line, 998 participated in the race safely," he said. Two died, however. And with Dr Webbon confirming that there are about 90,000 starts a year, that adds up to 180 horses dying at the courses during or as a result of racing, an average of more than three a week.

In the past, bulletins were published listing horses who had died on course or had been put down and would therefore no longer compete. That publication has now stopped. Dr Webbon, previously veterinary expert for the Jockey Club, said deaths and injuries had been logged by vets since 2000, and were now kept on a national database. "The figure in 2005 was the lowest number of fatal injuries on the courses since we started recording in this way. We keep extremely accurate records. Whenever the RSPCA asks for the figures we show them immediately, because it is a welfare association that wants to make racing as safe as possible for its participants."

But the RSPCA will not release the details because of an agreement with the Jockey Club, which ran the sport until last week. And a spokesman for the Jockey Club said the information would not be made public because Animal Aid "would use any specific figures as a potential tool for their cause, which is to see jump racing banned".

Animal Aid wants yesterday's Grand National to be the last, because jump racing is more dangerous to horses than the flat and Aintree is the most demanding course. The group says only a third of fatalities happen on race day. "They result from a broken leg, back, neck or pelvis; fatal spinal injuries; exhaustion, heart attack or burst blood vessels. The other victims perish from training injuries or are killed after being assessed by their owners as no-hopers." Fewer than half of the 16,000 foals bred every year go racing: the rest are sold for other uses or killed for pet food, according to Animal Aid. The group's director, Andrew Tyler, said: "The fact of equine deaths is concealed from the public. People think racing is an attractive, safe, amusing flutter. If we can show them that it is like betting on bullfighting then opinions will change."

David Muir, equine consultant to the RSPCA, takes a more moderate view. He has been consultant on the development of a new veterinary centre at Aintree and been instrumental in changing the fences on the course to make them safer. They now curve up to their full height so that hooves are less likely to get caught, and the tops are made of stacked pine fronds that fall off when knocked. Speaking out on the windswept course, where he was inspecting the fences before the first race, Mr Muir said: "Race courses will never be safe. Anything that involves jumps is not safe, because something can go wrong that has not been anticipated - but racing is a fact of life so we want to do as much as we can to help the horses."

The RSPCA has called for all hurdles - the 3ft 6in fences used at many courses including Cheltenham - to have their wooden frames removed from the top, so that horses can hit the brush without going down. It is possible to heal a clean fracture in a horse's leg, said Mr Muir, but if the injuries were "catastrophic" and the animal was in too much pain to be moved, then screens would be put up. While the race went on elsewhere the horse would be given a lethal injection or shot in the head. "You never see this on the television," he said.

More people than ever want to own race horses. The pressure is on to run more minor races so that owners can recoup some of their costs with prize money. Some horses that do not make it in flat racing are also sent over jumps for the same reasons. The HRA is expecting a report on whether modern horses bred for flat racing speed are weaker than the old-fashioned jumpers.

"I would like to see more backside and more bone," said Mr Muir, "although the scientists say that I am wrong and it is the quality of bone that counts. But my gut feeling is that when I think back to horses like Red Rum - big strapping racers with big bums - I feel comfortable. And when I look at some of the lighter horses going over fences I am not comfortable. More muscle and more stamina would mean more of them getting round safely."

Back at the HRA, Dr Webbon insisted that Britain led the world in research into how horses were injured, and the results were published in scientific journals. He added: "There is always going to be an element of risk, but I am sure the horses like to race. The natural reaction of wild horses is to gallop in a group. If it is natural behaviour then, in human terms, one has to assume they are enjoying it."