Mage won the 149th Kentucky Derby as America’s most celebrated race was overshadowed by the death of seven horses in the build-up.
Two horses, Chloe’s Dream and Freezing Point, died hours before Saturday’s race at Churchill Downs in Louisville.
Earlier in the week trainer Saffie Joseph Jr was suspended after two of his horses died.
“It is with the utmost sadness that we report these tragic fatal injuries,” race organisers said.
“Churchill Downs is unwavering in our commitment to the health and wellbeing of equine safety.”
As well as Parents Pride and Chasing Artie – both trained by Joseph Jr – Wild on Ice, Take Charge Briana and Code of Kings also died this week.
Animal rights group Peta said that, given the number of deaths, they had urged Churchill Downs to close the track in order to implement stronger safety protocols.
Favourite Forte was among the horses removed from the race early on Saturday, leaving only 18 runners, the smallest field since 2020.
Mage, a 15-1 shot ridden by Venezuelan Javier Castellano and trained by Gustavo Delgado, triumphed ahead of Two Phil’s and Angel of Empire, one of the pre-race favourites.
The Grand National was marred by the deaths of three horses across the three-day event in April.
The start of that race was delayed by 14 minutes after animal rights activists entered the track, while Hill Sixteen died after falling at the first fence.