Any horse entered for racing must be present on the grounds as follows, except with the prior approval of the official veterinarian:

(1) A first time starter must be present on the grounds two hours prior to the first post time or five hours prior to the post time of the race the horse is entered for racing, whichever is earlier.

(2) A horse that has previously started must be present on the grounds five hours prior to the post time for the race the horse is entered for racing.