In last April's Grand National, just 19 horses in the 40-strong field completed the gruelling course.
Dooneys Gate and Ornais suffered fatal injuries during the race, prompting Animal Aid to liken the race to Spanish bullfighting.
Aintree Racecourse and the British Horseracing Authority (BHA) this week announced the interim findings of their review into the 2011 John Smith's Grand National meeting.
The findings of the Grand National Review Group relate specifically to the Grand National course and its fences, which it said would be "subject to a balanced package of modifications with the aim of enhancing safety for competitors".
The changes follow expert analysis of all races run on the Grand National course since 1990, when the course was significantly remodelled.
The British RSPCA and World Horse Welfare were consulted, and the review group received input from leading trainers and jockeys.
The modifications will be in place before the next race on the Grand National course, the Becher Chase on Saturday, December 3.
Aintree Racecourse managing director Julian Thick said the safety and welfare of horses and riders was the top priority at the course.
"This is the latest stage in our continuous drive to make the Grand National Course as safe as possible.
"The Grand National," he said, "is an unparalleled challenge over four miles and four furlongs and this unique event is the most famous race in the world.
"It is not possible to completely eliminate risk in horse racing. However, I am confident the course changes we are announcing today will, over time, have a positive impact.
© TB Murray
Animal Aid noted that nine horses have been killed racing in the Aintree Grand National during the last decade.
It said the racing regulator was therefore expected to come up with significant course improvements, but it described them as nothing more than ineffectual tinkering.
"Aintree, the British Horseracing Authority and racing in general see the enormous amount of negative publicity associated with the two equine fatalities at this year's event as a public relations disaster and these measures are fashioned with a view to quelling public disquiet rather than saving horses' lives, Animal Aid's horse-racing consultant Dene Stansall said.
"Animal Aid's detailed analysis of the Grand National over the years and the severe problems it continues to present, despite endless changes, leads us to the firm conclusion that the Grand National is an un-reformable, anachronistic and immoral spectacle that should never be run again."
The group said the race was run over four-and-a-half miles, with the crowded field of 40 horses called upon to jump 30 challenging fences.
"A new analysis of the history of the race published by Animal Aid reveals that, in recent years, the risk of a horse dying in the race has increased rather than diminished, despite much heralded 'improvements'," the group said.
It said the measures "fall depressingly short of any genuine attempt to address the carnage that is a regular feature of the Grand National - a race that routinely sees fewer than half the runners finish and, on average, one death every year."
However, Jamie Stier, director of raceday operations and regulation for the BHA, described the course changes as sensible and balanced.
He said it was a strong package of track changes that will enhance rider and equine welfare.
The BHA launched a wider review of all aspects of the 2011 John Smith's Grand National in April 2011, which is ongoing. It aims to explore all available options to reduce manageable risk to horses and riders in the race. The results will be published in October.
During a calendar year, five races take place over the Grand National course over varying race distances. These are the John Smith's Fox Hunters' Steeplechase (2m 5½f), the John Smith's Topham Chase (2m 5½f) and the John Smith's Grand National (4m 4f) at the Grand National meeting plus the Grand Sefton Chase (2m 5f) and the Becher Chase (3m 2f) in autumn.
The course changes announced are:
1. The landing side of Becher's Brook (fence six on the first circuit and fence 22 on the second circuit) will be re-profiled to reduce the current drop (i.e. the difference in height between the level of the ground on takeoff and landing) by between 10cm (4 inches) and 12.5cm (5 inches) across the width of the fence. This will provide a more level landing area for horses. After the work is complete the drop will be about 25cm (10 inches) on the inside of the course and 15cm (6 inches) on the outside of the course. This difference in drop from the inside to the outside of the fence is being retained to encourage riders to spread out across the width of the fence and also to retain the unique characteristics of Becher's Brook. The height of the fence will remain unaltered at 4 feet 10 inches (1.47 metres).
2. Levelling work will also be undertaken on the landing side of the first fence (fence 17 on the second circuit) to reduce the current drop and provide a more level landing. By doing so, this amendment aims to avoid catching out horses that may 'over-jump' the (first) fence in the early stage of the race. The height of the fence will remain unaltered at 4 feet 6 inches (1.37 metres).
3. The fourth fence will be reduced in height by 2 inches to 4 foot 10 inches (1.47 metres). It was identified during the review that fence four and fence six (Becher's) were statistically more difficult to jump than other fences in all races over the National fences and this is the reason for this change.
4. The height of toe boards on all National fences will be increased to 14 inches (36cm). Toe boards are the orange board, positioned at the base of the fence and provide a clear ground line to assist horses in determining the base of the fence.