Short Heat Stress as an Immunostimulant in Chicks

The effect of 1 hour exposure of seven 1-week-old chicks to heat stress (41.5-42.5°) on their antibody titre after antigenic stimulation with E. coli bacteria was assessed. Exposure to heat 24 or 96 hours after immunisation resulted in a significant increase in antibody titres while heat treatment 42 or 72 hours after vaccination caused a non-significant increase in antibody titres. Heat exposure for 2 hours, 24, 48, 72 or 96 hours after immunisation either with E. coli or sheep red cells (SRBC) resulted in significantly increased antibody titres. When a number of antibody forming cells (against SRBC) in the spleens were tested, heat treated chicks showed no significant increase compared with the non-treated group. Heat-exposed chicks phagocytised Staphylococcus aureus bacteria (as measured by their disappearance from the blood) more rapidly than the non-treated group.