This experiment was conducted to compare the effects of multi-strain probiotic at various inclusion levels on performance, intestinal morphology, gut microflora and hematology in broiler chickens infected with Salmonella Typhimurium (ST). A total of 120 1-day old Ross 308 broiler chickens were distributed into 20 floor pens and reared for 10 days under 5 experimental treatments including a cornsoy basal diet with no probiotic (Control), or 0.5 g (0.05%), 1 g (0.1%), 1.5 g (0.15%) and 2 g (0.2%) probiotic/kg diet. Chickens were infected orally with ST at the second day of the experiment. Broilers under 0.15% of probiotic had higher body weight gain compared to other treatments. Probiotic supplementation, except at 0.05%, significantly improved feed conversion ratio. The use of 0.1 and 0.15% probiotic reduced the population of Salmonella in the ileum. The lowest heterophil: lymphocyte ratio was observed in 0.15% of probiotic, although 0.1 and 0.2% of probiotic significantly reduced this ratio compared to control group as well. Adding 0.15% of probiotic to the basal diet increased (P < 0.05) the ileal villus height to crypt depth ratio as well as villus height in the ileum, jejunum and duodenum. According to the present results, especially for body weight gain and salmonella counts in the ileum, adding 0.15% of probiotic in broiler chickens diet can be used for effective control of ST infection.

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