ARSD 20:04:20:81. Excuse of injured horse from starting post

If, after reaching the starting post, a horse is so badly injured that it is impractical or impossible for the horse to run in a race, the starter or official veterinarian may recommend to the stewards that the horse be scratched. If a horse is scratched, the start must be delayed until the mutuel department is notified and a change of odds is made.