Jockey Club puts limit on book size for stallions

The Jockey Club board of stewards has, for the first time, adopted a rule that limits the number of mares allowed to be bred to some Thoroughbred stallions in North America, it announced Thursday. The rule puts a cap of 140 mares bred annually for stallions born in 2020 or after. The Jockey Club put no cap on stallions born before 2019.

The new rule, as stated in a press release issued Thursday, states: “The total number of broodmares bred per individual stallion whose year of birth is 2020 or thereafter shall not exceed 140 per calendar year in the United States, Canada, and Puerto Rico.”

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By phrasing the rule as per calendar year rather than per breeding season mares bred within North America but on Southern Hemisphere time later in the year will still count toward the cap. The Jockey Club said that it will be modifying its Report of Mares Bred forms and other related documents to recognize the amendment.

The Jockey Club first announced that it was considering a rule limiting stallions’ books last September because of concern over “the narrowing of the diversity of the Thoroughbred gene pool.” Over the ensuing months, the Jockey Club has heard feedback from breeders, owners, and others with interests in the industry. Although the cap number, 140, is the same as initially proposed, the original rule under consideration would have phased in that cap depending on the year in which a stallion entered stud, rather than the stallion’s age.

The first crop of colts affected by the rule would be 4-year-olds in the 2024 breeding season. However, the effects of the rule could be seen earlier than that, as buyers consider colts’ residual values as stallion prospects at the 2021 yearling sales.

According to The Jockey Club’s Report of Mares Bred for the 2019 season, 44 stallions covered 140 mares or more in North America. All but three of those stand in Kentucky, representing 13 different farms. The number of stallions covering 125 or more mares increased from 62 in 2018 to 65 in 2019. There was a 7 percent increase in the number of mares bred to stallions with a book size of 125 or more in 2019 when compared to 2018 reports; a 9 percent decrease in mares bred to stallions with a book size between 100 and 124; and a continuing decrease down that scale.

The busiest stallions in North America in 2019 were Triple Crown winner Justify and globe-trotting Breeders’ Cup Juvenile Turf winner Mendelssohn, who both covered 252 mares in their first season at stud. Both stand at Coolmore’s Ashford Stud. Both are sons of Scat Daddy, and both shuttled to Coolmore Australia later in the year.