The present invention feeds pigs for meat with drinking water containing ultrafine bubbles of air by using a drinking water supply device 1 installed in a pigsty. This drinking water supply device 1 is provided with: a bubble water tank 2 for storing water containing ultrafine bubbles of air; a bubble water preparing device 3 that adds the ultrafine bubbles of air to the water from the bubble water tank 2; a second bubble water tank 4 that stores the ultrafine bubble water; a mixed fluid tank 5 for storing a mixed fluid of the ultrafine bubble water and a plant extract-mixed fermented liquid; a fermented liquid water tank 6 for storing an aqueous solution of the plant extract-mixed fermented liquid; and a water tank 7 for storing tap water. The liquids in the tanks are respectively guided to first to fourth farming areas A1, A2, A3, and A4, and are supplied to the pigs for meat by a water supplier 8.