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<p>The overall objective is to evaluate the efficacy of dietary modulation of antimicrobial peptide (AMP) synthesis in the control of foodborne pathogens in the chicken. The central hypothesis is that strategies to enhance the production of AMPs will confer on chickens the capacity to fight off infections, enhance survival, and reduce bacterial shedding. We plan to test the hypothesis and accomplish the overall objective by pursuing the following three specific objectives: </p>
<p>1) Search for AMP-inducing dietary factors, </p>
<p>2) Investigate the efficacy of selected dietary factors in protecting animals and reducing bacterial shedding, and </p>
<p>3) Study the molecular mechanisms of AMP induction by selected dietary factors. </p>
<p>It is our goal to develop a truly innovative, cost-effective strategy to augment animal immunity and disease resistance with no reliance on conventional antibiotics, which cause an increasing public health concern over the development of antibiotic resistance.</p>
<p>NON-TECHNICAL SUMMARY:<br/> The widespread use of antibiotics at sub-therapeutic levels in the animal industry has been criticized for the contamination of food products and the environment with unwanted antibiotic residues and potential emergence and dissemination of microorganisms that are resistant to these agents. To reduce antimicrobial resistance and to maintain optimal animal health without the use of conventional antibiotics, we sought to explore the potential for dietary modulation of innate immuity in the control and prevention of important foodborne pathogens using the chicken as an animal model. Such an immune-boosting approach is expected to be broadly applicable in the control and prevention of other pathogens in all other food animal species, offering great potential of enhancing animal biosecurity and production efficiency, while minimizing the use of
antibiotics and emergence of drug-resistant pathogens.
<p>APPROACH:<br/> A range of vitamins, essential amino acids, and trace minerals, and fatty acids will be tested individually or in combination in chicken cells. The dietary factor(s) that gives strong antimcrobial peptide (AMP) gene induction in vitro will be confirmed in chickens by a series of dose-response and time-course experiments. The top three dietary factors that are among the most potent in inducing AMP gene expression will be fed to chickens following experimental infections with S. enteritidis. Animal survival and bacterial titer in the cecum and feces will be examined. The top 1-2 dietary factors that are most potent in inducing AMP gene expression in vitro and reducing bacterial shedding in vivo will be selected for further investigation of the molecular mechanisms. Promoter analysis of inducible AMP genes will be conducted. Signaling pathways involved in
dietary factor-mediated AMP induction will be screened and studied for their significance. Next-generation sequencing will also be employed to profile the transcriptional response of the chicken cells to selected dietary factors.
<p>PROGRESS: 2011/10 TO 2012/09<br/>OUTPUTS: After screening of a range of dietary factors including fatty acids, vitamins, essential amino acids, and trace minerals, we found that short-chain fatty acids (SCFAs) are among the most potent agents in inducing HDP gene expression in different chicken cell lines and and in live chickens as well. Furthermore, HDP induction is largely in an inverse correlation with the aliphatic hydrocarbon chain length of free fatty acids, with SCFAs being the most potent, medium-chain fatty acids moderate, and long-chain fatty acids marginal. Additionally, three SCFAs, namely acetate, propionate, and butyrate, exerted a strong synergy in augmenting HDP gene expression in chicken cells. Consistently, supplementation of chickens with a combination of three SCFAs resulted in a further reduction of Salmonella enteritidis in the cecum as compared
to feeding of individual SCFAs. More importantly, free fatty acids enhanced HDP gene expression without triggering proinflammatory interleukin-1? production. PARTICIPANTS: Dr. Guolong Zhang managed and coordinated the entire project and participated in the in vitro and in vivo experiments. Dr. Jerry Ritchey at Oklahoma State University helped with pathology of the chicken infection studies. Dr. Hyun S. Lillehoj at USDA-ARS provided the chicken HD11 macrophage cell line for in vitro analysis. Dr. Susan Lamont at Iowa State University provided Salmonella enteritidis type 13a for chicken infection studies. TARGET AUDIENCES: Livestock producers, immunologists, and nutritionists will all benefit from the advances of this research. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.