Developmental Regulation of chicken cathelicidins in the lung. Lungs were harvested from broiler chickens of indicated age and subjected to RNA isolation and real-time PCR analysis of the expression of four cathelicidins. Fold differences in the cathelicidin expression level among different days after hatching were calculated relative to the expression level on day 2 (for fowlicidins 1 to 3) or day 7 (for cathelicidin B1) using GAPDH as a reference gene. Each bar represents mean ± standard error of 3 to 5 chickens. The statistical significance was analyzed using one-way ANOVA followed by Tukey’s Test.