The Jockey Club, board of stewards 'continue to study' stallion cap

The Jockey Club board of stewards on Monday announced that it is continuing consideration of a rule to limit the annual breeding of individual stallions.

Concerned with the narrowing of the diversity of the Thoroughbred gene pool, the board had previously revealed in September that it may phase in a cap of 140 mares bred per individual stallion per calendar year in North America.

“We are grateful for the many thoughtful comments in response to our September proposal," Monday's statement reads. "The stewards are considering those comments as we continue to study the cause and effects of decreasing diversity of the Thoroughbred gene pool and finalize a rule to protect the breed’s health and welfare.”

The Jockey Club is the breed registry for Thoroughbreds in North America. Since its founding 125 years ago, it has been dedicated to the improvement of breeding and racing of Thoroughbreds, focusing on improvements to the integrity, health, and safety of the sport.

As has been widely reported, the size of the North American foal crop has diminished significantly, from 37,499 in 2007 to the 20,500 estimated for 2020. 

In 2007, 37 stallions reported in excess of 140 mares bred each from a total of 3,865 stallions. By 2010, that number had declined to 24. Since then, the number has nearly doubled to 43 stallions reporting 140 or more mares bred from a population of stallions that now stands at less than one-half that of 2007. 

On the mare side, in 2007, 5,894 mares (9.5% of the total) were bred by stallions that covered more than 140 mares. By 2019, 7,415 mares (27% of the total) were covered by stallions with books of more than 140, a threefold increase.  

The combination of these changes has resulted in a substantial increase in the percentage of foals produced by a discreet segment of stallions — signaling a worrisome concentration of the gene pool.

Phasing in of the cap was proposed as so:

• Stallions entering stud service for the first time in 2020 would be exempt from the 140 limit through the 2023 season

• Stallions that entered stud service in 2019 would be exempt through the 2022 season

• Stallions that entered stud service in 2018 would be exempt through the 2021 season

• Stallions that entered service in 2017 or prior would be subject to the 140 cap as of January 1, 2021