Long-term exposure of chickens to three levels of social stress.

Cockerels were kept in environments characterized by high (HSS), medium (MSS), or low (LSS) levels of social stress for 3 or 4 months. Chickens raised in an environment of low light intensity (LSS) gained more weight than did those raised under natural lighting. Ability of chickens to produce antibody in response to antigen was greatly reduced, 2(15.4) in the LSS group to 2(3.4) in the HSS group, 1 day after chickens were moved from the LSS environment into the HSS environment. Normal responsiveness returned within 1 week. No long-term environments affected antibody production. After 3 months, chickens in the LSS environment had reduced weight gain and resistance to Escherichia coli infection compared with birds in the HSS environment. Chickens in the MSS environment, compared with those on the HSS and LSS environments, had greater weight gains, superior feed efficiencies, medium plasma corticosterone levels, a better negative correlation between antibody responsiveness and RBC antigens, and better resistance to Mycoplasma gallisepticum challenge. All parameters except antibody responsiveness were such that long-term exposure to HSS or LSS environments appears to be detrimental.