The Jockey Club today released Report of Mares Bred (RMB) statistics for the 2023 breeding season. Based on RMBs received through October 18, 2023, The Jockey Club reports that 867 stallions covered 26,597 mares in North America during 2023.

The Jockey Club estimates an additional 2,500 to 3,500 mares will be reported as bred during the 2023 breeding season.

The following table shows the number of covering stallions and the number of mares bred over the past 10 years in North America as reported to The Jockey Club by mid-October for each year.

RMB statistics, sortable by stallion, mares bred, or state, for all reported stallions in 2023 are available through the Fact Book section of The Jockey Club’s website at

Kentucky traditionally leads North America in Thoroughbred breeding activity. During 2023, Kentucky’s 199 reported stallions covered 16,953 mares, or 63.74% of all of the mares reported bred in North America. The number of mares bred to Kentucky stallions increased 1.58% compared with the 16,689 reported at this time last year.

Of the top 10 states and provinces by number of mares reported bred in 2023, in addition to Kentucky, stallions in New York, Ontario, and West Virginia covered more mares in 2023 than in 2022, as reported at this time last year. The following table shows the top 10 states and provinces ranked by number of mares reported bred in 2023 and includes Oklahoma and Indiana, which were included in the top 10 in 2022:

Florida-bred Golden Pal had the highest number of mares bred in 2023 with 293, followed by Epicenter (262), Practical Joke (252), Jack Christopher (247), and Uncle Mo (234).

There were 14 stallions with a book size of 200 or more that covered a total of 3,213 mares in North America in 2023 as reported through October 18, which is 12.1% of all coverings reported.

The 45 stallions with books of 150 or more covered 8,588 mares, which is 32.3% of all mares reported bred. For comparison, reports submitted by October 10, 2013, show that one stallion covered more than 200 mares in North America, which represented 0.6% of the total for that year. Those reports also show 19 stallions covered 150 or more with a total of 3,205 mares in the 2013 breeding season, which equates to 9.4% of all mares reported bred in 2013 as of October 10.

The following table shows the number of stallions that covered 200 or more mares and the number of mares bred by those stallions in North America as reported to The Jockey Club by mid-October of each year.

In addition, Report of Mares Bred information on stallions that bred mares in North America is available through report 36P or a subscription service at

Return to the Oct. 27 issue of Wire to Wire