RESUMEN
This study was designed to compare the effect of the prebiotic and antimicrobial growth promoter [AGP] on the growth performance, blood constituents, intestinal bacteriology and histomorphometric parameters as well as humeral immunity of broiler chicks. A total of 90 unsexed commercial Cobb chicks were randomly assigned to 3 dietary treatments [control, AGP and prebiotic groups], each group contains 30 chicks. Each group subdivided into 3 replicates, 10 chicks each, and was reared for 42 days. The prebiotic supplemented group showed a significant improvement in growth performance parameters in comparison to the control and AGP-supplemented groups. Total leukcocytic count, lymphocyte percent, total protein, total globulin and gamma globulin were significantly increased in the broilers fed on prebiotics. Moreover, prebiotics supplementation significantly reduced heterophil percent, heterophil/ lymphocyte ratio [H/L ratio], albumin/globulin ratio, aspartate and alanine aminotransferase [AST and ALT], uric acid and creatinine compared to the AGP-supplemented and control groups. The AGP-supplemented group exhibited a significant reduction in the total aerobic count when compared to the control and prebiotic-supplemented groups. However, the prebiotic supplemented group showed a significant reduction in the coliform count when compared to the control and antibiotic supplemented groups. The prebiotic supplemented group induced a significant increase in the villus height [VH] all over the small intestine. In addition, it induced a significant increase in villus height: crypt depth ratio in the duodenum and jejunum in comparison to the control and antibiotic supplemented groups. However, there were no significant differences among the different groups regard to the crypt depth [CD] in the duodenum and jejunum. Prebiotics could be considered as safe and effective antimicrobial alternatives for broiler chicks' growth performance, immunity and intestinal bacteriology and morphology