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Author: Erika Shirer | Major: Animal Science | Semester: Spring 2025
In January of 2023, I began an undergraduate research project in the Animal Science Department under Dr. Charles Maxwell and Dr. Tsungcheng Tsai. Our overall goal was to examine whether dietary fiber and fiber-degrading enzymes introduced to swine would modulate their gut microbiome during periods of clinical illness.
The purpose of this research trial was to determine whether dietary fiber (soyhull + sugar beet pulp) and a fiber-degrading enzyme, stimbiotic (Signis), could modulate the gut microbiome leading to growth performance improvement in weaning pigs challenged with F18 E. coli. Dietary fiber has been shown to promote a healthy GI tract bacteria community while fiber-degrading enzymes act to reduce plant fiber complexities. This allows for improvement of the efficacy of digestive enzymes and to increase nutrient bioavailability and fiber accessibility to bacteria, which in turn increases oligosaccharide production and health-beneficial metabolites. Adding these to dietary treatments can alleviate the deleterious effects of proinflammatory responses.
In the spring of 2024, virulence genes of the isolate were qualified using multiplex polymerase chain reaction (PCR) to detect and characterize pathogenic E. coli. Through PCR, the use of multiple primer pairs in a reaction mixture allowed for the amplification of multiple target sequences. From there, we were able to identify the genotypic characterization of E. coli isolates from pigs challenged with F18 E. coli. The live E. coli count was not different between the dietary treatments. Of 466 colonies, most colonies were devoid of the virulence genes tested in this study, while the colonies that expressed the F18 gene also presented LTb, Stb, and Stap simultaneously. In addition, of the colonies that did not express the F18 gene; 21, 19, and 21 of these colonies co-expressed LTb, Stb, and Stap, respectively.
Pigs fed high fiber diets (HF and FS) decreased the percentage of F18 encoded E. coli than pigs fed low fiber diets (CC and CS), while pigs fed stimbiotic (CS and FS) had higher percentage of F18 encoded E. coli than diets devoid of Signis (CC and HF). Pigs fed CC and HF had similar percentages of F18 encoded E. coli, while pigs fed FS and CC had a lower percentage of E. coli encoded with F18 gene than pigs fed CS. Results of the trial exhibited that dietary fiber sources benefited average daily gain (ADG) and average daily feed intake (ADFI) shortly after the challenge. Additionally, Signis increased ADG in pigs fed the control diet and feed efficiency was improved in control and fiber diets.
There were no significant differences in the total E. coli count and the percentage of virulence genes expressed in live E. coli colonies differently between high fiber diets and Signis, suggesting a different mechanism may be involved in restoring ADG in pigs challenged with ETEC. Trial results indicated that the effect of Signis on ADG in nursery pigs exposed to live F18 E. coli depends on the source of dietary fiber. Additionally, improvement in feed efficiency was proven to be consistent.
Results of this study demonstrated that high fiber and stimbiotic exerted a distinguished percentage of virulence genes expressed in live E. coli colonies suggesting a different mechanism on restore ADG when challenged with ETEC.
In March of 2024, Dr. Tsungcheng Tsai, my committee member, and I traveled to Madison, Wisconsin for the 2024 American Society of Animal Science (ASAS) Midwest Section Meeting. While there, I presented in an undergraduate poster competition regarding the “Effect of fiber and stimbiotic on growth performance and the gut microbiome in pigs challenged with F18 enterotoxigenic Escherichia coli (ETEC)”. The intended purpose was to present how pathogenic Escherichia coli affects growth and development during the early weaning period of the swine and to determine the effectiveness of dietary fiber sources and fiber-degrading enzymes on the sustainability of the ETEC challenge. In the spring of 2025, I will again attend the 2025 ASAS Midwest Section Meeting in Omaha, Nebraska. There, I will compete in the Undergraduate Student Oral Paper Competition and will present updated and more extensive research after data collection was completed.
As for the future, I plan to attend veterinary school and subsequently graduate with a Doctor of Veterinary Medicine degree. Veterinary practices surrounding shelter, wildlife, small animal, and livestock medicine have recently piqued my interest. By exploring these specialties through shadowing, hands-on experience, and research I have been able to familiarize myself with the diverse responsibilities that different specialties are responsible for in their day-to-day practice. While I was not raised in an agricultural environment, my participation in laboratory, clinical, and production settings has confirmed my intent and desire to pursue a career in veterinary medicine.