In its annual Report of Mares Bred (RMBs) released Tuesday, The Jockey Club estimates that the 2027 foal crop will be 16,500. That's down 500 from the estimate for the 2026 crop.The numbers released by The Jockey Club follow a troubling trend. The foal crop has declined every year since 2015, when there were 21,529 registered foals.The foal crop projection is computed by using Reports of Mares Bred (RMBs) received to date for the 2026 breeding season. RMBs are to be filed by Aug. 1 of each breeding season. For the RMBs received through Oct. 1, 2026, The Jockey Club reports that 670 stallions covered 23,932 mares in North America during 2026.Seventeen stallions covered 200 or more mares. The previous high mark was in 2022 when 16 stallions covered 200 or more mares.Sierra Leone, who stands at Coolmore America, led all stallions, having been bred to 293 mares. That is the first book of mares that he has covered. Tiz the Law, last year's leader, was next at 288. He also stands at Coolmore, as does Citizen Bull, who checked in third having been bred to 261 mares. Gun Runner (250) was next, followed by Gunite (236).Rounding out the top 10 are: Not This Time (230), Drain The Clock (227), Locked (226), Vekoma (224) and Girvin (223).Coolmore had four horses in the top 10, while Gainesway was next with two.Mindframe was bred to 187 mares, a record for a Claiborne stallion.As is always the case, Kentucky again led North America in Thoroughbred breeding activity. During 2026, Kentucky's 187 reported stallions covered 16,677 mares, or 69.6% of all mares reported bred in North America.With 1,490 mares having been bred in California that state edged Florida (1,273) for second place on the list. With racing no longer taking place in the Chicago area, Illinois breeders took a major step back. Only 13 mares were bred in the state.Standing in Florida at Pleasant Acres Stallions, Gulfport was the most active stallion outside of Kentucky. He was bred to 167 mares.Of the RMB reports received, 180 mares were part of the Mare Incentive Program, which waives registration fees for certain 2027 foals of mares that meet criteria defined by The Jockey Club. This initiative was announced in December 2024 to stimulate interest in mares that appear to have left production.The report of Mare Incentive Program mares is available through Interactive Registration and is filterable by 12 data elements, including sire, dam sire, age, money earned, and class of race achieved.RMB statistics, sortable by stallion, mares bred, or state, for all reported stallions in 2026 are available through the Fact Book section of The Jockey Club's website.The post Foal Crop Drops Again; Sierra Leone is Most Active Sire appeared first on TDN | Thoroughbred Daily News | Horse Racing News, Results and Video | Thoroughbred Breeding and Auctions.