You mention that this is a "personal livestock" trailer. By livestock, I assume you are referring to farm animals versus it being a horse trailer? Horses can be pets and people often transport them around to various events. But sounds like you are talking about moving farm animals across state lines in some trailer that is larger than your normal trailer since you mentioned size. So sounds to me like you are engaged in Interstate commerce and driving a vehicle large enough to require a commercial license when you engage in interstate commerce, yet as long as you stay in your own state you aren't engaging in interstate commerce so maybe you don't need the commercial license there?