Immune Tissue Weight
The effect of increasing levels of FO on immune tissue weight (as a percentage of final BW) in broiler chickens is shown in Table 3. Results show that FO did not affect the weights of the spleens of broiler chickens. Chickens fed diets containing 50 g/kg of FO had significantly greater thymus weights compared with chickens fed 0, 30, or 60 g/kg of FO (P < 0.001). Chickens fed a diet containing 50 and 60 g/kg of FO had significantly lower bursa weights (P < 0.001) than those of chickens fed diets containing no FO or 30 g/kg of FO. In addition, the bursae were thinner in appearance compared with control bursae and those from chickens fed diets containing less FO (not shown).