Location: Agroecosystems Management Research
2019 Annual Report
Objectives
The objectives of the project are to develop an understanding of the interrelationships between non-antibiotic feed additives and pathogen translocation and shedding in growing pigs, obtain critical measures of oxidative stress in growing pigs and reproducing swine, and develop interventions to reduce or prevent pathogen colonization and disease in swine in an effort to maximize production efficiency but minimize environmental impact.
Objective 1: Evaluate alternatives to antibiotics (butyric acid, resistant starch, inulin, etc.) for maintaining growth performance and reducing intestinal bacterial translocation and shedding in growing pigs.
Objective 2: Determine the inherent variation in oxidative stress measures in breeding and lactating gilts, and correlate to measures of sow lifetime productivity.
Objective 3: Identify markers associated with oxidative stress and correlate to changes in pig growth and feed intake, using peroxidized soybean oil as the inducer of oxidative stress.
Objective 4: Determine whether vaccination of swine with a Salmonella DIVA vaccine can prevent/reduce colonization and improve growth following transmission of Salmonella from actively shedding pigs.
Approach
Alternatives to antibiotics for growing pigs will be assessed through the evaluation of compounds which have the potential to affect gastrointestinal function and microbial ecology which would, therefore, affect pig performance. Compounds to be evaluated include resistant starch, soluble dietary fiber, short- and medium-chain fatty acids, phytogenics, inorganic minerals, and beta-glucans; all of which have been suggested to affect gastrointestinal function and microbial ecology. Determination of the inherent variation in oxidative stress measures in breeding and lactating gilts will be assessed by collecting biological samples from gestating and lactating sows at 4 critical time points during these reproduction phases, and measuring key oxidative stress parameters (DNA, protein, and lipid damage) as well as antioxidant status (plasma vitamin E). In growing pigs, identification of markers associated with oxidative stress and impact on pig performance will be assessed by feeding peroxidized soybean oil to nursery, grower, or finishing pigs. Peroxidized soybean oil will be generated by heating soybean oil at 45°C for 288 h, 90°C for 72 h, or 180°C for 6 h, in comparison to unheated (22.5°C) soybean oil. Oxidative stress will be assessed measuring key oxidative stress parameters (e.g., DNA, protein, and lipid damage) as well as antioxidant status (e.g., plasma vitamin E) while performance effects will be measured by growth over a predetermined period. An attenuated Salmonella vaccine was previously designed and constructed to provide broad protection against numerous Salmonella serovars in food-producing animals. A Salmonella transmission trial will be performed in swine to determine whether vaccination against Salmonella can prevent or reduce Salmonella colonization and improve growth performance following exposure to pigs actively shedding Salmonella.
Progress Report
Research on feeding peroxidized soybean oil to nursery pigs indicated that consumption of peroxided lipids resulted in a reduction in animal growth rate and increased measures of oxidative stress. Additional research to increase the concentration of lipid peroxidation products in soybean oil was successful and when fed to growing pigs resulted in a 25% reduction in daily gain compared to pigs fed unperoxidized soybean oil. In broilers, the reduction in daily gain was only 10%, indicating that pigs and broilers respond differently to the consumption of peroxidized soybean oil. Research on feed additives proposed to increase butyrate concentrations in the large intestine of pigs was initiated, with preliminary results indicating that there was no change in cecal and colon butyrate concentrations and no change in pig performance compared to pigs fed diets not containing in-feed additives.
Salmonella enterica serovar I 4,[5],12:i:- is the fourth most frequent cause of human salmonellosis in the U.S. and 68% of serovar I 4,[5],12:i:- isolates are multidrug-resistant (MDR; resistance to 3 or more antimicrobial classes), accounting for the most common MDR Salmonella serovar (35%). In 2015, a multistate outbreak of MDR serovar I 4,[5],12:i:- occurred due to consumption of contaminated pork. Genomic analysis of a pork outbreak-associated isolate of MDR serovar I 4,[5],12:i:- demonstrated the presence of two genetic insertions, an antimicrobial resistance module (encoding resistance to 4 antimicrobial classes) and metal tolerance island for copper, arsenic, and silver. Phenotypic analysis indicated that pork outbreak-associated serovar I 4,[5],12:i:- has increased tolerance to copper and arsenic compared to wildtype Salmonella enterica serovar Typhimurium. In addition to metal tolerance genes, DNA mobilization and transfer genes are also present on the metal island and allowed transfer of the island to another Salmonella strain that did not initially contain the metal tolerance island. These experiments demonstrate horizontal gene transfer of the metal tolerance island from pork outbreak-associated Salmonella enterica serovar I 4,[5],12:i:- to another Salmonella strain, resulting in the recipient acquiring an increased tolerance to metals.
Accomplishments
1. Identification of porcine microRNAs during Salmonella infection. Swine infection due to a microbial pathogen triggers a coordinated immune response that is regulated at multiple points to tailor the magnitude of the reaction to the specific microorganism. During the response, immune genes are expressed producing messenger RNAs (mRNAs) that are translated into functional proteins to facilitate the reactions. Porcine microRNAs (miRNAs) are small, untranslated RNAs that bind to mRNAs as an additional level of regulatory control. ARS researchers in Ames, Iowa, identified 50 porcine miRNAs with significant differential expression over a 7-day period following inoculation of swine with the foodborne pathogen Salmonella enterica serovar Typhimurium (Salmonella Typhimurium). The immune response of individual pigs to Salmonella Typhimurium is variable based on swine genetics, and identification of porcine miRNAs provides another tool for characterization of the porcine response to Salmonella infection to assist in development of interventions to mitigate pathogens in food-producing animals.
Review Publications
Lindblom, S.C., Gabler, N.K., Bobeck, E.A., Kerr, B.J. 2019. Effect of oil source and peroxidation status interactively affects growth performance and oxidative status in broilers from 4 to 25 days of age. Poultry Science. 98:1749–1761.
Schweer, W.P., Burrough, E.R., Patience, J.F., Kerr, B.J., Gabler, N.K. 2019. Impact of Brachyspira hyodysenteriae on intestinal amino acid digestibility and endogenous amino acid losses in pigs. Journal of Animal Science. 97:257-268. https://doi.org/10.1093/jas/sky393.
Kerr, B.J., Curry, S.M., Lindblom, S.C. 2019. Digestibility of energy and caloric value in nursery pigs fed commercially available lipids. Applied Animal Science. 35:291-297. https://doi.org/10.15232/aas.2018-01835.
Shippy, D.C., Bearson, B.L., Cai, G., Brunelle, B.W., Kich, J., Bearson, S.M. 2018. Modulation of porcine microRNAs associated with apoptosis and NF-kappaB signaling pathways in response to Salmonella enterica serovar Typhimurium. Gene. 676:290-297. https://doi.org/10.1016/j.gene.2018.08.044.
Bearson, S.M., Bearson, B.L., Sylte, M.J., Looft, T.P., Kogut, M.H., Cai, G. 2019. Cross-protective Salmonella vaccine reduces cecal and splenic colonization of multidrug-resistant Salmonella enterica serovar Heidelberg. Vaccine. 37(10):1255-1259. https://doi.org/10.1016/j.vaccine.2018.12.058.
McCafferty, K.W., Bedford, M.R, Kerr, B.J., Dozier III, W.A. 2019. Effects of cereal grain source and supplemental xylanase concentrations on broiler growth performance and cecal volatile fatty acid concentrations from 1 to 40 d of age. Journal of Applied Poultry Research. 98(7):2866-2879. https://doi.org/10.3382/ps/pez032.
Holman, D., Bearson, B.L., Allen, H.K., Shippy, D.C., Loving, C.L., Kerr, B.J., Bearson, S.M., Brunelle, B.W. 2018. Chlortetracycline enhances tonsil colonization and fecal shedding of multidrug-resistant Salmonella enterica serovar Typhimurium DT104 without major alterations to the porcine tonsillar and intestinal microbiota. Applied and Environmental Microbiology. 85(4):e02354-18. https://doi.org/10.1128/AEM.02354-18.
Hung, Y.T., Hanson, A.R., Urriola, P.E., Johnston, L.J., Kerr, B.J., Shurson, G.C. 2019. Addition of tert-butylhydroquinone (TBHQ) to maize oil reduces lipid oxidation but does not prevent reductions in serum vitamin E in nursery pigs. Journal of Animal Science and Biotechnology. 10:51. https://doi.org/10.1186/s40104-019-0362-5.
