The current study aimed to eva‎luate the effect of prebiotic and acidifier supplementation on the performance, relative organ weights, immune responses, gut microbial population, and short-chain fatty acids (SCFA) in the cecum of broiler chickens, alongside the strength of the tibia bone. A total of 1,260 one-day-old (Ross 308) meal broiler chickens were employed and randomly assigned to 9 treatments with 5 replicates, each containing 28 birds, in a 3×3 factorial design. The dietary treatments involved three levels of prebiotic (0, 0.5, and 1 g/kg feed) and three levels of acidifier (0, 0.75, and 1.5 g/kg feed) throughout the 42-day trial period. Weight gain, feed intake, and feed conversion ratio were periodically recorded. At the experiment's conclusion, one bird from each replicate was randomly selected and slaughtered. The relative weights of the carcass and immune organs were determined as percentages of body weight, and the pH of the gizzard and ileal contents, the microbial population at the terminal ileum, SCFA levels in the cecum, and the properties of the left tibia were analyzed. Antibody titers against Newcastle disease virus, influenza, and sheep red blood cells were assessed at specified intervals post-vaccination. The findings indicated that prebiotic supplementation during the first 10 days reduced the feed conversion ratio, while the highest daily weight gain was observed at the 0.75 g/kg acidifier level (p<0.05). Interaction effects revealed that the greatest daily weight gain occurred in the treatment with the highest levels of both acidifier and prebiotic, and the lowest feed conversion ratio was associated with the treatment containing 1 g/kg prebiotic and 0.75 g/kg acidifier in the diet (p<0.05). During the growth period, experimental treatments did not significantly impact performance indices (p>0.05), although in the final period, feed intake was influenced by interaction effects (p<0.05). No significant differences were observed between treatments across the entire trial period (p>0.05). No significant differences in organ weights were detected in the main or interaction effects (p>0.05). In terms of gut microbial population, no significant effect was observed on the growth of lactic acid-producing bacteria in the main effects, and the lowest levels of these bacteria were found in the control treatment under interaction effects. Antibody titers against sheep red blood cells (SRBC), total and IgG, were only affected in the first period by the experimental treatments (p<0.05). In examining the morphology of the intestine, an increase in prebiotics resulted in longer villi. Among the treatments, the control group exhibited the shortest villus length (p<0.05). The experimental treatments also influenced the length, weight, and strength characteristics of the left tibia (p<0.05). Overall, the study's findings suggest that incorporating prebiotic and acidifier compounds in the diet of broiler chickens can enhance intestinal morphology, promote the proliferation of lactic acid-producing bacteria in the gut, and improve the health of the birds' gastrointestinal system.

محمد صدقي

اميرحسين مهدوي , فريبرز خواجعلي

سعيد انصاري مهياري , صبيحه سليمانيان زاد