Effects of mannan oligosaccharide, Bacillus clausii, and their synbiotic supplementation on growth performance, humoral immunity, intestinal morphology, and ghrelin gene expression in broiler chickens

This study evaluated the effects of a prebiotic (mannan-oligosaccharide, MOS), a probiotic (Bacillus clausii), and their combinations on growth performance, immune response, intestinal morphology, and ghrelin gene expression in broiler chickens. Two hundred fifty day-old Hubbard chicks were randomly allotted to five treatments (control, prebiotic, probiotic, Combo-I 50:50, Combo-II 100:100), each with five replicates of 10 birds. Combo-II supplementation improved body-weight gain and feed conversion ratio during the starter (p = 0.0256 and 0.0428), grower (p = 0.0425 and 0.0483), and finisher phases (all p < 0.05). Newcastle disease and infectious bursal disease antibody titers increased (p = 0.0445 and 0.0456) and mortality declined (p = 0.0428) in all supplemented groups, with zero mortality in the probiotic and combination treatments. Serum IgM, IgA, and IgG concentrations were elevated (p < 0.05), and duodenal villus height, villus width, crypt depth, and villus-height/crypt-depth ratio were significantly improved (all p < 0.05) in Combo-II birds. Ghrelin mRNA expression was up-regulated in pancreas and proventriculus (p < 0.05), peaking in Combo-II. These results demonstrate that full-dose prebiotic + probiotic supplementation optimizes broiler growth, immunity, gut morphology, and metabolic gene expression.