“Sales yard” includes any livestock yard, pen, corral, building, premises, or conveyance in which swine are assembled for sale, resale, exchange, or transfer by any owner or his agent. It does not, however, include any ranch premises where swine are assembled for sale, resale, exchange, or transfer by any owner or his agent in ordinary ranch-to-ranch transactions, or where swine are fed and fitted for slaughtering purposes only.