Growth Response of a Salmonella typhimurium Poultry Isolate to Zinc Addition

It has been shown that induced molting by complete feed withdrawal increases Salmonella horizontal transfer in laying hens and contamination in eggs. Zinc-containing diets have been used as an alternative means to induce molt in laying as a management while avoiding feed withdrawal. It is not known if the zinc in these molt diets would inhibit Salmonella spp. growth and therefore potentially minimize the Salmonella spp. infection in individual hens. The objective of this study was to examine the effects of zinc concentration on a primary poultry isolate of Salmonella typhimurium growth from either nutrient rich or minimal media after inoculation. zinc sulfate (ZnSO4) concentrations (0.67%, 2.01%, 3.35%, 4.69%, and 6.03%) were added to either 5ml of tryptic soy broth (TSB) or M9 broth after inoculation of overnight fresh culture. The growth of S. typhimurium poultry isolate in individual tubes at 37 ◦C was measured by as optical density (A600) on a spectronic 20D spectrometer. Growth rate was determined by linear regression of change in natural logarithm of A600 during exponential growth. Growth rate of S. typhimurium poultry isolate was significantly (P<0.05) decreased by the presence of zinc sulfate in M9 at concentrations greater than 2.01%. Zinc added to M9 broth at the same concentrations was much less inhibitory to S. typhimurium poultry isolate growth rates. The results indicate that the higher concentrations of zinc addition may be effective by inhibiting Salmonella spp. growth.