Bacterial infections cause significant economic losses in the broiler industry throughout the production cycle. It is known that CpG-ODN stimulated innate immune activities and enhanced the resistance to infectious pathogens in chickens. In this study, the effectiveness of CpG-ODN was evaluated in organ colonization by Salmonella enteritidis at different ages of chickens. Pre-treatment of 2-day old chickens with CpG-ODN by subcutaneous injection and subsequent challenge with S. enteritidis 3 h after treatment resulted in significant reduction of organ invasion by S. enteritidis. In a second experiment, these chickens were repeatedly treated with CpG-ODN at day 20, and 24 h later were orally infected with S. enteritidis. There was no significant reduction in organ invasion by S. enteritidis compared to PBS treated controls. In a third experiment, five-day old chickens were treated with CpG-ODN and 24 h later orally infected with S. enteritidis. There was no reduction in organ invasion compared to PBS treated control group. Our study shows that CpG-ODN increase resistance against S. enteritidis invasion in broiler chicken in early age.

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