Abstract: The disclosed system comprises one or more stationary dispensers associated with drinking fountains for farm animals, for dispensing predetermined doses of drugs or nutrients, operating in cooperation with a plurality of portable units constructed for individual animals. The portable units are designed to interact electronically with a stationary dispenser to control the amount and timing of the doses. The stationary dispenser includes in circuit relation, an interrogator-transmitter, a reply receiver, and a liquid dispenser responsive to the reply receiver. Each portable system comprises a coded passive transponder, a timer, and a memory element. When an animal comes within range of the stationary dispenser, its portable transponder is interrogated. A coded reply is sent by the animal's transponder indicating whether animal has received a dose within a preceeding preselected time interval. If a positive reply is received by the stationary dispenser circuit, no further action is taken.