Effect of dietary propolis (PR) supplementation on the productive performance of broiler chickens challenged with Escherichia coli (EC) infection. (a) final body weight (FBW) at 42 d of age, (b) total feed intake (TFI), (c) body weight gain (BWG), and (d) feed conversion ratio (FCR). Bars express the mean (n=10) with standard error (SE). Means with dissimilar letters significantly differ at p < 0.05. Treatment groups: C, control group without PR supplementation or EC challenge; EC, group without PR supplementation but challenged with EC; PR, group supplemented with PR but not challenged with EC; PR+EC, group supplemented with PR and challenged with EC.