Buyer should have probably got that for you when he bought the calves- now you are at the mercy of the previous owner...You need to get ahold of that previous owner and see if they fall under the drug free/all natural and then make up an affidavit for him to sign...I'm not sure but I believe USDA has a special one for some programs- but most I have seen were made up by the feedlot--Most usually ask for birth period (like March 1-June 1) , country, state, and county ran in, any feed additives given, any shots given, verification that they've had no antibiotics or implants, any ID markings ( hot iron brand, eartags, etc.) ...
Some I've seen- usually for the specialized lean meat programs also included breed/breeds of bulls and cows ( Future Beef required 1/4 exotic blood)....