North American Jockey Club adopts rule restricting stallions to 140 mares

The Jockey Club of North America's board of stewards has adopted a final rule limiting book sizes for individual stallions born from 2020 onwards to 140 mares in a calendar year.

Stallions born in 2019 or before will be exempt from the cap.

The Jockey Club's Principal Rules and Requirements of the American Studbook have been amended accordingly and are effective from Thursday.

The new rule will have a deep impact on the businesses of farms who stand the most popular stallions in future.

In an illustration of how book sizes and earning potential could be dramatically inhibited, Justify and Mendelssohn, the joint-busiest sires in the US last year according to the Jockey Club's Report of Mares Bred, each covered 252 mares at Ashford Stud at fees of $150,000 and $35,000 respectively.

Six other stallions covered 200 or more mares in North America in 2019 – Into Mischief (241), Uncle Mo (241), Goldencents (239), Bolt D'Oro (214), Munnings (202) and Practical Joke (200).

A further 38 sires covered 140 or more mares in the US that year.

Those stallions are exempt from the new rule but studs will not be able to accept as many applications for successful or promising names of the future.

That crucial part of the new rule, applicable to the US, Canada and Puerto Rico, represents a significant change from Jockey Club proposals announced last year.

Originally it was suggested that stallions entering stud service for the first time in 2020 would be exempt from the 140 limit until the 2023 season; those that entered stud in 2019 would be exempt until the 2022 season; stallions that entered stud service in 2018 would be exempt until the 2021 season; and that stallions that entered service in 2017 or earlier would be subject to the 140 cap from 2021.

Instead, the new rule applies to colts born from 2020 onwards, meaning stallion farms will not have to restrict books until 2023 at the earliest, if any happened to retire after a successful juvenile season.

The Jockey Club first announced last September that it was considering a book size cap due to concerns over the limiting of the thoroughbred gene pool and that it would consult with the industry.

The move was welcomed in some quarters but with anger in others, with Ned Toffey – general manager of Spendthrift Farm, which stands Into Mischief, his son Goldencents and Bolt D'Oro – telling the Louisville Courier Journal last month: “I think it’s fair to say that if they were to institute this, I’d be shocked if it wasn't challenged legally.

“We don’t feel that a true problem has been identified or that what’s been posed would even be the right solution if you do accept the fact that there’s a problem.”

The Jockey Club said in a statement that it was "grateful for the many thoughtful comments in response to its September rule proposal.

"The stewards carefully considered those comments in formulating a rule that will promote diversity of the thoroughbred gene pool and protect the long-term health of the breed.

"The Jockey Club will continue to maintain the Principal Rules and Requirements of the American Studbook in keeping with its mission to ensure the health of the thoroughbred breed."

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