Mo. Rev. Stat. § 196.150
It shall hereafter be unlawful for any person, firm, association, or corporation to sell or offer for sale, either in wholesale or retail lots, any horse or mule meat under the guise or name of beef or any other animal flesh under the guise or name of any meat or meat product except that which in fact and truth it may be, without having attached thereto, a tag or other mark for identification plainly and legibly setting forth the true name of the animal from which such meat or flesh was taken or without having prominently displayed over or in conjunction with such meat or flesh, a legible sign or placard containing the true name of the animal from which the same was taken and without also advising the purchaser thereof by verbal, written or printed notice of the true name of the animal from which such meat or flesh was taken.
§ 196.150, RSMo