Plasma steroid tendency, social environment and Eimeria necatrix infection.

Chickens from a line selected for high levels of plasma corticosterone when housed in an environment faciliating considerable social interaction were more resistant to Eimeria necatrix infection than those from a line selected for low levels of plasma corticosterone housed in an environment that minimized social interaction. Individuals in the high steroid group had a more active phagocytic defense and fewer schizonts than those in the low steroid group.