Research Project: Physiological, Microbiological, and Nutritional Mechanisms to Maintain Animal Productivity in the Absence of Antibiotics

Location: Agroecosystems Management Research

2023 Annual Report

Objectives
To develop an understanding of intestinal integrity in nursery pigs, understand mechanisms involved in bacterial gene transfer using in vitro and ex vivo methodology, define mechanisms by which phenolic and pigment feed additives affects growth and physiological factors in nursery pigs, and determine the effects of lipid composition and quality affects the caloric value of such products in growing pigs; all in an effort to maximize production efficiency but minimize environmental impact. Specific objectives are: Objective 1: Develop in vitro and ex vivo models for assessing intestinal integrity. Objective 2: Evaluate the mechanism of bacterial gene transfer, and identify modulators, for a metal tolerance element containing genes for tolerance to copper, silver, and arsenic. Objective 3: Define mechanisms by which phenolics and pigments modulate animal growth, intestinal function, immune competence, microbial ecology, and bacterial gene transfer in swine. Objective 4: Determine how lipid composition and quality affects energy digestibility and growth performance parameters in growing pigs; and subsequently develop equations to predict digestible energy values for lipids in growing pigs.

Approach
Models for assessing intestinal integrity will be accomplished by three separate methods: through the feeding of different levels of dietary crude protein, by implementing different levels of feed restriction, and by inducing heat stress and hypoxia to nursery pigs, all of which have been suggested to affect gastrointestinal function. Mechanisms of bacterial gene transfer and identification of modulators associated with copper, silver, and arsenic will be accomplished by conjugation experiments using both in vitro and ex vivo methods, with a conjugation reporter system used to monitor horizontal transfer of integrative and conjugative gene elements from a donor to a recipient. Mechanisms by which phenolics and pigments modulate animal growth, intestinal function, immune competence, microbial ecology, and bacterial gene transfer will be accomplished by feeding nursery pigs diets containing either phenolics or pigments for a period of 42 days after which key criterion associated with each of these indices will be evaluated. To determine how lipid composition affect energy digestibility, saturated fatty acids with carbon chain lengths from 8 to 18 and the blending saturated fatty acids with an unsaturated fatty acid will be fed to nursery pigs for 28 days, during which fecal samples will be taken to assess total tract energy digestibility. Modeling will then be used to develop equations to predict digestibility energy values for each lipid as affected by saturated carbon length and concentration.

Progress Report
In support of Objective 1, the animal trial evaluating different levels of dietary crude protein on intestinal integrity has been completed with laboratory analysis of biological samples under way. In addition, collaborative research with colleagues at Iowa State University in Ames, Iowa, is also underway to delineate the effect of dietary protein on animal performance. This data will be important to livestock producers on the impact of high protein diets on intestinal integrity, immune competence, and growth production due to the increased availability of soybean meal for use in feed formulations due to the demand of soybean oil for increased biofuels in the United States. Strains of Salmonella enterica serovar Infantis from poultry (broiler chickens and turkeys) that have multiple antimicrobial resistance and metal tolerance genes have recently increased in prevalence. Most of the antimicrobial resistance and metal tolerance genes are present on a large, mobile plasmid of emerging S. Infantis (pESI) that can be transferred by conjugation to other bacterial strains. The pESI plasmid also contains potential virulence genes including yersiniabactin biosynthesis and uptake for iron acquisition, and a unique fimbriae for cellular attachment. In support of Objective 2, a genetic model for investigation of the pESI plasmid has been developed. This model system will allow investigation of horizontal gene transfer between bacterial strains and construction of gene knockout mutants to determine the role of individual gene classes (antimicrobial resistance, metal tolerance, yersiniabactin biosynthesis and uptake, and a unique fimbriae) in Salmonella physiology and poultry colonization. In support of Objective 4, both a swine and poultry trial have been completed evaluating the impact of carbon lengths of fatty acids on their energy digestibility. This trial included medium chain fatty acids (i.e., carbon chain lengths of 8 to 12 carbons long) and long chain fatty acids (i.e., carbon chain lengths of 14 to 18 carbons long). This data will be important to livestock producers for finding alternative lipids for use in feed formulations as the price has increased and the availability decreased ion lipids typically used in animal feeds due to many lipids being used for increased biofuels production in the United States.

Accomplishments
1. Resistant starch is not acceptable as an alternative to antibiotics in livestock diets. With the U.S. ban on the use of clinically important antibiotics for animal growth promotion in 2017, there is a need for the development and evaluation of alternatives to antibiotics for maintenance of gastrointestinal function and rates of performance in swine production. Resistant starch is a prebiotic that supports the growth of beneficial bacteria in the gastrointestinal tract, including microorganisms that produce short chain fatty acids, which promote favorable intestinal health to limit colonization by opportunistic bacterial pathogens and may improve mineral digestibility and animal performance. ARS researchers in Ames, Iowa, determined that administration of resistant corn or potato starch to pigs had minimal impact on intestinal short chain fatty acids, and did not alter intestinal function, mineral digestibility, or animal performance. This is important to the swine industry indicating that resistant starch is not an equivalent alternative to in-feed antibiotics to support growth of beneficial bacteria in swine feeding programs.

Review Publications
Kerr, B.J., Trachsel, J.M., Bearson, B.L., Loving, C.L., Bearson, S.M., Byrne, K.A., Pearce, S.C., Ramirez, S.M., Gabler, N.K., Schweer, W.P., Helm, E.T., De Mille, C.M. 2022. Evaluation of digestively resistant or soluble fibers, short- and medium-chain fatty acids, trace minerals, and antibiotics in nonchallenged nursery pigs on performance, digestibility, and intestinal integrity. Journal of Animal Science. 100(11). Article skac282. https://doi.org/10.1093/jas/skac282.
Fan, M.Z., Kerr, B.J., Trabue, S.L., Yin, X., Yang, Z., Wang, W. 2022. Swine nutrition and environment. In: Chiba, L.I., editor. Sustainable Swine Nutrition. 2nd edition. Hoboken, NJ. Wiley. p.547-601.
Wilson, V.C., McCormick, S.P., Kerr, B.J. 2023. Feeding thermally processed spray-dried egg whites, singly or in combination with 15-acetyldeoxynivalenol or peroxidized soybean oil on growth performance, digestibility, intestinal morphology, and oxidative status in nursery pigs. Journal of Animal Science. 101. Article skac429. https://doi.org/10.1093/jas/skac429.
Trabue, S.L., Kerr, B.J., Scoggin, K.D., Andersen, D., van Weelden, M. 2022. Swine diets: Impact of carbohydrate sources on manure characteristics and gas emissions. Science of the Total Environment. 825. Article e153911. https://doi.org/10.1016/j.scitotenv.2022.153911.
Trachsel, J.M., Bearson, B.L., Kerr, B.J., Shippy, D.C., Byrne, K.A., Loving, C.L., Bearson, S.M. 2022. Short chain fatty acids and bacterial taxa associated with reduced Salmonella enterica serovar I 4,[5],12:i:- Shedding in swine fed a diet supplemented with resistant potato starch. Microbiology Spectrum. 10(3). Article e0220221. https://doi.org/10.1128/spectrum.02202-21.
Wilson, V.C., Ramirez, S.M., Murugesan, G.R., Hofstettler, U., Kerr, B.J. 2022. Effects of feeding variable levels of mycotoxins with or without a mitigation strategy on growth performance, gut permeability, and oxidative biomarkers in nursery pigs. Translational Animal Science. 6(3). Article txac126. https://doi.org/10.1093/tas/txac126.
Demille, C.M., Burrough, E.R., Kerr, B.J., Schweer, W.P., Gabler, N.K. 2022. Dietary pharmacological zinc and copper enhances voluntary feed intake of nursery pigs. Frontiers in Animal Science. 3. Article 874284. https://doi.org/10.3389/fanim.2022.874284.
Loving, C.L., Bearson, S.M., Bearson, B.L., Kerr, B.J., Kiros, T.G., Shippy, D.C., Trachsel, J.M. 2022. Effect of dietary ß-glucan on intestinal microbiota diversity and Salmonella vaccine immunogenicity and efficacy in pigs. Veterinary Microbiology. 278. Article 109648. https://doi.org/10.1016/j.vetmic.2022.109648.
Kerr, B.J., Pearce, S.C., Ramirez, S.M., Schweer, W.P., Gabler, N.K. 2023. Soluble corn fiber, resistant corn starch, and protected butyrate effects on performance, gastrointestinal volatile fatty acids, and apparent total-tract digestibility of calcium and phosphorus in nursery pigs. Journal of Animal Science. 101. Article skad022. https://doi.org/10.1093/jas/skad022.
Bearson, S.M., Trachsel, J.M., Bearson, B.L., Loving, C.L., Kerr, B.J., Shippy, D.C., Kiros, T.G. 2023. Effects of ß-glucan on Salmonella enterica serovar Typhimurium swine colonization and microbiota alterations. BMC Porcine Health Management. 9(7). Article 003024. https://doi.org/10.1186/s40813-023-00302-4.