- - - Department of Animal Sciences, College of Agriculture, Isfahan University of Technology, Isfahan, Iran.
- - - Department of Animal Sciences, College of Agriculture, Isfahan University of Technology, Isfahan, Iran.
- - - Department of Animal Sciences, College of Agriculture, Isfahan University of Technology, Isfahan, Iran.

To investigate the effects of newly introduced probiotic, prebiotic, and synbiotic, ۱۰۸۰ d-old broiler chickens were used in a completely randomized design with six treatments and six replicates of ۳۰ birds each. Dietary treatments were: basal diet (control), basal diet plus ۵۰۰ g of probiotic/ton (Probiotic-۵۰۰), basal diet plus ۵۰۰ g and ۳۰۰ g of probiotic/ton during days ۰-۲۴ and ۲۵-۴۲ of age, respectively (Probiotic-۵۰۰-۳۰۰), basal diet plus ۳۰۰ g of probiotic/ton (Probiotic-۳۰۰), basal diet plus ۱ kg of prebiotic/ton (Prebiotic), basal diet plus ۱ kg of synbiotic/ton (Synbiotic). Average daily weight gain and feed conversion ratio were only affected by dietary treatments during the starter period; the lowest average daily weight gain and the highest feed conversion ratio were recorded for the control treatments compared to the others. The antibodies titers (total, IgG, and IgA) against sheep red blood cells, and Newcastle and Influenza viruses were significantly (P < ۰.۰۵) increased by feeding diets containing all experimental additives compared with the control diet. The pH of the ileum decreased (P < ۰.۰۵) by using probiotic, prebiotic, and synbiotic in the diets. The highest number of lactobacillus and E. coli populations was observed in birds fed synbiotic and control diet, respectively. The height of villus in the jejunum and its ratio to crypt depth was higher in birds fed a symbiotic diet compared to birds fed probiotic or control diets (P < ۰.۰۵). Furthermore, the cecum concentration of short-chain fatty acids was greater in chickens fed diets containing probiotic, prebiotic, or synbiotic than the control chickens (P < ۰.۰۵). In conclusion, although dietary supplementation with probiotic, prebiotic, and synbiotic had no positive effect on growth performance parameters of broiler chickens, the use of these products could exert promising effects on poultry health.

Antibody titer, Jejunal morphology, microbial population, Short-chain fatty acid