This experiment was conducted to investigate the effects of olive leaf (OL) on immune response and some blood metabolites of broiler chickens. A total of 400 one-day-old broiler chicks (male and female) were randomly assigned to 5 experimental treatments with 4 replicates of 20 birds each. Birds of different treatments were given diets containing 0, 0.25, 0.5, 0.75 and 1% OL powder from 14 to 4...