Immunosuppression has historically cost the poultry industry in increased mortality and in performance factors during rearing. In addition, immunosuppression has had a negative impact on the ability of the poultry industry to process chickens due to associated health problems. Industry strategies for controlling immunosuppression are not consistent between broiler companies. The broiler industry is refining their strategies for controlling immunosuppression based on research and field observations. However, strategies to control immunosuppression are largely based on vaccination programs for broiler breeders and broiler progeny, and management to minimize stress during rearing.