More than 100 animal rights protesters have been arrested after some invaded the Grand National course and forced the start of the world’s most famous steeplechase to be delayed by a quarter of an hour.

About 70,000 fans were at Aintree to cheer the 8-1 favourite Corach Rambler to victory, but the day will be remembered more for the sight of dozens of protesters from Animal Rising using ladders to scale the barricades around the course before attempting to stop the race.

The group, which has pledged to “rise up and take direct action to see an end to animal suffering in all its forms”, appeared to come close to succeeding – with two of their members in pink T-shirts being bundled away as they attempted to use glue and locking devices to attach themselves to fences.

Merseyside police said that 118 people had been arrested for trying to delay the race and for public order offences beforehand.

The day was also marred by the death of Hill Sixteen after a first-fence fall, as well as Dark Raven in a race earlier on the card. Altogether, three horses died in the three-day meeting, following the death of Envoye Special on Thursday.

Dickon White, who runs Aintree Racecourse, said: “Hill Sixteen was immediately attended by expert veterinary professionals during the Grand National, but sadly sustained a fatal injury. Our heartfelt condolences are with his connections.”

Merseyside police said in a statement after the race: “Just after 5pm a large number of protesters attempted to gain entry on to the course. The majority were prevented from breaching the boundary fencing but nine individuals who managed to enter the course were later arrested by officers.”

However, that figure was disputed by a spokesperson for Animal Rising, who told the Observer that “at least 40 or 50” of its members had been initially detained by police.

The delay meant there was no pre-parade or national anthem and the race – which was due to start at 5.15pm – only got under way at 5.29pm. However, one protester said that direct action had been taken to raise awareness of the situation animals faced.

“We’re a nation of animal lovers, but the pain these beautiful creatures experience daily does not do that label justice,” she said. “We need to find ways of loving animals that don’t hurt them.

“I know everyone coming to Aintree to view the races today would say they love the horses. However, the suffering experienced by them should shock us all. That’s why I’ve decided to put my body between those horses and death on the racecourse, rather than gamble with their lives.”

Lucinda Russell, the trainer of Corach Rambler, said that in fact the protests had negatively affected the welfare of the horses as they prepared to race. “The protesters are just doing it for themselves,” she added.

The deaths of the horses were condemned by Animal Aid, which had been among the groups protesting outside the course. “Innocent race horses suffer at the hands of an industry focused on making money from their exploitation,” it said in a statement. “Aintree continues to be a prolific killer of horses.”

Protesters also closed the M57 motorway by gluing themselves to the tarmac, and drivers experienced delays of more than three hours. Police stopped traffic in both directions on the road running from the M62 motorway to the racecourse.

Earlier in the day about 150 protesters from multiple animal rights organisations stood in front of Aintree’s gates, many of them holding placards such as “You bet, they die” and “Protect Animals, Cancel the Grand National” as spectators arrived.

Terse words were also being exchanged between the police and some of those handing out leaflets, with protesters being told to move back because they were on private property but refusing to do so and citing their lawful right to protest. Shortly after two protesters were arrested on suspicion of conspiracy to cause public nuisance, including a 25-year-old woman from London.

Animal Rising later posted a video of one of their media team being arrested and carried away by three policemen. The group said she had been detained “for speaking out about the cruelty that is about to unfold on the track at Aintree”.

Another woman, 33, was arrested earlier on suspicion of conspiracy to cause a public nuisance in connection with potential disruption at the racecourse. The woman, from London, was arrested in the Greater Manchester area, police said.