Animal rights campaigners shouted "shame on you" to racegoers attending the final day of the Grand National meeting on Saturday.
Dozens of protesters stood outside Aintree Racecourse, holding placards that read "National disgrace" and "You bet, they die".
It comes after the deaths of four equines at this year's meeting.
Another demonstration is being held in London outside the offices of Channel 4, which is broadcasting this year's Aintree festival.
The two protests, organised by animal rights group Animal Aid, come as controversy continues to mar the sporting event.
This year's Grand National is the deadliest Aintree festival in five years after two horses died on opening day and another two died yesterday.
Both Gullinbursti and Minella Reception were fatally injured after falling at the notorious Becher’s Brook fence on Friday.
Ten-year-old Gullinbursti, who missed last season due to a tendon injury, somersaulted and landed on his neck during the Topham Chase.
Gullinbursti had to be humanely euthanised after his fall, Channel 4 said.
Minella Reception suffered a similar fall and was given veterinary attention but had to be put down.
On Thursday, Clonbanan Lad and Marasonnien, both 10 years old, sustained fatal injuries in the Fox Hunters Chase, which was just over two and a half miles long.
The last time the festival saw four horse deaths was in 2011.
Dene Stansall, Animal Aid’s horseracing consultant, said on Friday: “The Aintree authorities and the official industry regulator, the British Horseracing Authority, have sought, over the last two years, to lure the public into believing that equine deaths at Aintree were now to be thought of as a rarity in this modern age.
“But history shows that, over the long term, the Grand National Course continues to be a perversely harsh test for horses, and one that often proves lethal.
“Making horses race on that course does not add up to a sporting spectacle, but the most selfish form of animal abuse.”
This year’s fatalities means that 46 horses have died in the event since 2000.
Professor Chris Proudman, veterinary adviser at Aintree, said earlier this week: “You can never remove all risk completely from any sport, including horseracing”, adding “British racing has a fatality rate of less than 0.2%”.
No horses died during Saturday's races.