Reduction of cecal colonization and fecal shedding of Salmonella Typhimurium in broilers fed proprietary zinc- or manganese-amino acid complexes

Intestinal Salmonella colonization of chickens represents one of the most important food safety hazards. Mitigating this problem is challenging since Salmonella is a commensal in poultry. In this study, we assessed the ability of proprietary zinc-amino acid and manganese-amino acid complexes to reduce Salmonella colonization and shedding in commercial broilers receiving such trace minerals in the finisher diet. Broilers were orally challenged with Salmonella Typhimurium on five occasions between Day 1 and Day 20 of age. After confirming that the chicks were shedding Salmonella in the feces on Day 22, broiler chicks were fed a standard diet containing: proprietary zinc-amino acid complexes; proprietary zinc- plus manganese-amino acids complexes; ZnSO4+MnSO4; ZnSO4; or no additional supplements. Fecal samples were obtained on four occasions and were subjected to enumeration of Salmonella. Birds were euthanized on Day 42 and ceca were removed for enumeration of Salmonella. Salmonella fecal shedding and cecal colonization were significantly decreased in broilers fed Zn-amino acid complexes, when compared to broilers fed Control diets. Feed efficiency and body weight gain were greater in broilers fed proprietary Zn-amino acid complexes or proprietary Zn- plus Mn-amino acids complexes compared to birds fed the Control or ZnSO4+MnSO4 diets. Furthermore, real-time quantitative RT-PCR-based studies revealed enhanced expression of various cytokines, chemokines, tight junction proteins, and beta-defensins in birds fed the higher dose of the Zn-amino acid complexes. Thus, it appears that the Zn- and Mn-amino acid complexes reduce Salmonella carriage and improve feed efficiency possibly by optimizing the innate immune response to Salmonella and by improving gastrointestinal epithelial barrier.