All domestically-trained runners in Great Britain are subject to the new rule.
BBC Sport has revealed that racehorses entering Great Britain to race will need to be removed from the food chain starting January.
British Horseracing Authority (BHA), has changed the rules so that horses cannot be sent in abattoirs to get money to slaughter them for food.
James Given, director of Equine Health and Welfare at BHA, stated that transporting horses to an abattoir for them to be used as pets was not something they should allow in their sport.
A BBC Panorama investigation in July revealed that over 4,000 racehorses, some of which were once owned by and trained in Ireland, had been slaughtered in Great Britain since the start of 2019.
Racing authorities have indicated that 12% of them would have been killed in Great Britain based on data.
Given explained that the rule was changed to ensure that all racehorses were treated for injuries on racecourses with the best drugs.
For the moment, horses that have not been removed from the human food chain are not allowed to be given certain drugs such as the painkiller phenylbutazone or 'bute.
Horses can still be sent to an Abattoir to be put down humanely. However, they cannot be sold for food.
The BHA's veterinary panel proposed the rule in January. However, it needed to be approved by the board and rules committee of the organization, which was done last month.
This applies to all domestically-trained runners in Great Britain. It will not be accepted if entries have not been declared via the Weatherbys app or the horse's passport that the horse was not intended for human consumption.
It is intended to cover international runners. The BHA is currently in contact with other jurisdictions.
A leading welfare charity however warned that this is not the "welfare panacea" it may seem and warned that there could be an "underground market" that allows people to bypass the rules.
Given stated to BBC Sport that there are many welfare issues behind this. It is a wonderful development, I believe.
It is the result of work done by the Horse Welfare Board last year, which developed euthanasia guidelines as well as a decision-making tree for people who are going through a very difficult time.
"All four of the cornerstone stakeholder groups were consulted, and they all agreed that it was right and proper to do this. The Panorama programme highlights its necessity even more."
He stated that the transporting horses to an abattoir for sale to consumers should not be considered euthanasia. This is an approach that should not be tolerated in our sport. Therefore, it is a positive move to establish a rule prohibiting this practice.
"I'm confident that most British trainers, owners and managers agree with me on this point and have already observed this principle."
Panorama investigated the Panorama covert recording and raised concerns about horse slaughter at one of the UK’s largest abattoirs.
Another issue was that horses were being transported hundreds of kilometres from Ireland, and some had career-threatening injuries.
Panorama was told by Drury and Sons that they take great care to ensure animal welfare and refuse any form of abuse.
Roly Owers, chief executive of World Horse Welfare, told BBC Sport that "This is an intriguing development but it must be avoided as unintended consequences like any other change."
"Signing horses off the food chain isn't the welfare panacea that it may seem to be. It will be crucial for the BHA monitor the effects of this change and take appropriate action if necessary.
"Equally, this change will make it more urgent to have lifetime responsibility and traceability of all ex-racehorses as there will be no slaughterhouse.
"And until there's a robust digital horse identification system, there's still the risk that some racehorses might be entered fraudulently into the food chain in an underground trade that we know has grave risks for equine welfare.
