Effects of a probiotic on the growth performance, intestinal flora, and immune function of chicks infected with Salmonella pullorum

This study investigated the effects of a Lactobacillus paracasei KL1 and Lactobacillus plantarum subsp. plantarum Zhang-LL mixed probiotic on Salmonella-caused pullorosis in chicks. A total of 120 1-day-old Nongda no.3 dwarf chicks were randomly assigned to 4 treatments, with 6 replicates of 5 birds each. The treatments were blank group, Salmonella pullorum-infected group, probiotic treatment group, and probiotic prevention (PP) group. All birds (n=90) except those in the blank group were infected with S. pullorum on day 4. On day 14, the BW, ADG, mortality, pathology of tissue, cecum colony count, immune organ indices, cecal mucosa secretory IgA, and cytokines were investigated. The results showed that the chicks infected with S. pullorum were depressed and their BW reduced. The PP group had the highest ADG and lowest mortality rate (0%), whereas the S. pullorum-infected group had 37.50% mortality rate and lowest ADG. Pathologic sections showed that the probiotic treatment group had minor lesions but the PP group had no lesions in the ileum, cecum, and liver. Cecal Lactobacillus counts was the highest (P < 0.05) and Salmonella and Escherichia coli counts were the lowest (P < 0.05) in the PP group; Compared with the S. pullorum-infected group, the thymus and spleen indexes of the probiotic treatment group increased (P < 0.05), but they were unaffected (P < 0.05) in the bursa of Fabricius, whereas in the PP group, all the immune organs were increased (P < 0.05). Cecal mucosa secretory IgA and IL-4 were the highest (P < 0.05) and tumor necrosis factor a and interferon gamma were the lowest (P < 0.05) in the PP group; In summary, the Lactobacillus KL1 and L. plantarum Zhang-LL mixed probiotic effectively reduced the mortality of pullorosis in chicks, promoted the growth performance, regulated the balance of the intestinal flora, improved the immune function, resisted pullorosis disease, completely prevented chicks from pullorosis after infection, and reduced economy loss in the poultry industry.