A 3-year-old horse may belong at the Kentucky Derby or Preakness, but not on an endurance ride--or a limited distance ride, for that matter.

AERC's rule 3.1 explicitly states, "The equines entered in the full distances must be at least 60 months old at the time of the ride." For limited distance rides, rule L3.1 notes that the age requirement is a minimum of 48 months.

Age is determined from the actual foal date. That means you cannot enter an equine in a ride even a day shy of his actual birthday.

Underage horses are automatically discovered when ride results are entered into the AERC database, and the rule infraction is sent to the Protest & Grievance Committee for resolution when the period underage is more than 30 days. For violations less than this period - the horse is marked Disqualified in the records and the owner is notified that a second violation will will be sent to the Protest & Grievance Committee.

If you register your equine with AERC, be careful not to ride him in an AERC event until he is old enough--5 for endurance rides (50 miles or more) or 4 for limited distance rides (less than 50 miles).