31. Where the veterinarian administers to a horse a drug, a medication or any other substance which may yield positive results when analyzed or where the veterinarian recommends that such drug, medication or substance be administered to a horse, the veterinarian must indicate to the trainer of the horse, as the case may be:(1) the quantity of drug, medication or substance administered;
(2) the quantity of drug, medication or substance to be administered;
(3) the period of time during which the taking of an official sample of the drug, medication or substance administered or to be administered is likely to yield positive results.