Most mares bred to one stallion in 1 year

The world record for the most mares bred to one stallion, in one year, is 521. The stallion, SJ's Photo, is owned by Kosmos Horse Breeders, Littlestown, Pennsylvania, USA.  From  February - December 2001, 521 mares all over the world (USA, Canada, Germany, Holland, Denmark, Sweden, Norway, Italy, Australia, New Zealand) were inseminated, naturally or artificially, all resulting in pregnancies. The northern hemisphere breeding season is from the 15 February - 15 July, the Southern hemisphere is from 1 October - end of February. Thus, mares were inseminated throughout the year, according to different breeding seasons. Therefore, the record is based on most in 1 year, rather than most in 1 breeding season. SJ's Photo is a standardbred stallion and is one of the world's leading trotting stallions. He was named after his sire, Photomaker, and mare, Sassy Jane.