Effects of cold stress on immune responses and body weight of chicken lines divergently selected for antibody responses to sheep red blood cells.

Effects of cold stress (CS) on the immune system of chicken lines divergently selected for high (H line) and low (L line) antibody responses to SRBC next to a randombred control (C) line were studied. Three- to four-week-old growing chicks of the three lines were feed-restricted at 80% ad libitum and subjected to CS at 10 degrees C continuously for 7, 5, 3, 1, or 0 d prior to immunization with keyhole limpet hemocyanin (KLH). Specific and natural antibodies were measured in the three chicken lines subjected to or not subjected to various durations of CS prior to immunization. In addition to antibodies we also measured in vitro lymphocyte proliferation as a measure of cell-mediated immunity (CMI), zymosan-induced reactive oxygen intermediates (ROI) production as a measure of phagocytosis, and BW gain as a measure of production trait. In general, significantly higher antibody responses to KLH and natural antigens were found in the H line as compared to the other two lines. Specific antibody responses to KLH were not significantly affected by CS, but an acute transient increase in natural antibody titers to ovalbumin was found in H line birds subjected to 1 d of CS, which was not found in C or L line birds. On the other hand, an acute significant increase in natural antibody titers to lipopolysaccharide (LPS) was found in C and L line birds subjected to 1 d CS but not in H line birds. Cold stress enhanced the ROI production. In addition, 7 d of CS significantly enhanced cellular immunity in vitro, but no significant line effects with respect to cellular immunity were found. BW gain was negatively affected by CS, especially when CS was applied for longer periods. We concluded that birds responded immediately to CS with enhanced innate (phagocyte and natural antibody) immunity, irrespective of genetic background. When CS is prolonged, the cellular adaptive immune response is affected also. Although reallocation of energy was not measured, our data suggested that under limited conditions (e.g., restricted feeding) with simultaneous stress (e.g., CS), growth and cellular immunity were more sensitive than thermoregulation and humoral immunity. With respect to vital life traits, thermoregulation may have first priority followed by adaptive cellular immunity, humoral immunity, and BW gain. The relationships between immune responses and adaptation to stress are discussed.