Heat production during the induction of an immune response to sheep red blood cells in growing pullets.

Total and activity-free heat production (Hp) were determined in light and dark periods of the day during the induction of the immune response. A small but significant increase in Hp appeared 4 days after immunization, 1 day after the rise in hemagglutinin antibody was detected. The Hp of the immunized birds remained above that of phosphate buffered saline-injected birds for the remainder of the experiment.