(CNN) It has been published since 1791 and survived two world wars, the Irish potato famine and the conflict in Northern Ireland.
But Brexit is threatening to handicap the "mother" of all horse stud books.
Until now, the UK and Ireland have operated as one entity in terms of racing and breeding thoroughbred racehorses with all pedigree information recorded in the General Stud Book.
Could Britain's exit from the European Union end 227 years of joint history? As with most things Brexit, no one is quite sure.
"The Stud Book is the book where the breeding of horses has been recorded for centuries," Brian Kavanagh, chief executive officer of governing body Horse Racing Ireland, told CNN by phone.
"There are twice as many foals born in Ireland as there are in Britain, and they are recorded in a single stud book and that just shows you how integrated the business is."
For example, British racecourses and owners are heavily dependent on a steady supply of racehorses bred in Ireland, while Irish breeders rely on British buyers to purchase their bloodstock.
"If it had to happen that the stud books were separated and the British and the Irish stud books were separated, that is not impossible," said Kavanagh. "It would be a change of something that's been there for centuries and there is no real desire for it."
Although racing had been ongoing for hundreds of years, it wasn't until the 18th century that thoroughbreds were developed in Britain, when English mares were crossed with Arabian and other stallions to create animals with great endurance for distance racing, according to NewScientist.com.
James Weatherby was the first to publish the breeding records of throroughbreds, and the General Stud Book has been published by Weatherbys ever since, according to the Weatherbys website.
A new volume comes out every four years. The most recent one, volume 48, was published last year, meaning the next edition is scheduled for 2021.
The UK is set to leave the EU on Friday March 29, 2019.
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Since the June 2016 Brexit referendum, the British horse racing and breeding industries have been working closely with Irish and French counterparts "in making representations to the relevant stakeholders in domestic governments, European parliamentarians and [European] Commission officials," Weatherbys spokesman Nick Craven told CNN in an email.
"Ireland and Britain are considered a single epidemiological unit for equine health purposes," he said, adding that onging EU and UK recognition of the Stud Book would be for the "clear benefit" of both parties.
Kavanagh is also hoping for a good ending.
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"Hopefully nothing will happen and we will be able to come up with a solution where things don't change and we can continue to record the horses in the single stud book," he said.