Abstract: A spray vaccination apparatus using a positive-displacement peristaltic pump to deliver vaccinating liquid to the spray nozzles. The vaccinating liquid is contained in a plastic bag similar to an IV bag, and a flexible plastic tube extends from the bag to the spray nozzles. A peristaltic pump engages this tube for positive-displacement pumping. The pump is actuated for a predetermined increment of time, whenever a tray of baby chicks is inserted into the spray vaccination apparatus, thereby spraying the chicks with vaccinating liquid for a predetermined interval. The spray nozzles preferably are equipped with valves which open only while the pump operates, providing a relatively abrupt onset and termination of spray. All elements of the liquid delivery system remain closed and sealed from the atmosphere, thereby maintaining a sterile condition throughout. These components preferably are disposable, eliminating the need to cleanse the system components periodically.