They are raced at three years old because that is when they are full grown and are almost adults.
Thoroughbreds, 3 years old and older
A colt but generally only until 2 yrs old beacuase they are raced at 3
Races for 3 year old thoroughbreds are restricted by entry conditions "for 3 year olds". The Triple Crown (Kentucky Derby, Preakness, and Belmont) are the most commonly known races for 3 year olds.
The Cesarewitch is a flat horse race in Great Britain open to thoroughbreds 3 years or older.
Three-year-olds have been raced for centuries.
Only 3 year old Thoroughbreds are allowed to run in the Kentucky Derby. No other age is allowed.
Mozart was 3 years old the entire time that he was 3 years old.
Red Rose hence the nickname "the run for the roses" open ONLY to 3 year-old Thoroughbreds. KDJudy Valparaiso, IN
The Kentucky Derby is raced on a 1 1/4 mile track.
If a human is 3 years old, then a dog is 21 years old.
If a cat is 3 years-old. They are 29 years-old in human years.
21