Assessing the Effects of Genetic Selection for Porcine Circovirus Type 2 Resistance or Feed Additives on Nursery and Grow-Finish Pig Performance

The swine industry is ever evolving as it strives to produce healthy, wholesome pork for consumers. As such, the industry is constantly looking for ways to improve production and reduce costs. This includes using novel feed ingredients to reduce cost and improve animal health, genetic selection for increased performance, and vaccines to attenuate or prevent illness. Research plays a significant role in assessing the effectiveness of these strategies. Overall, the objective of this thesis was to assess how genetic selection, vaccines, and feed additives may impact growth performance, health, nutrient digestibility, and the microbiome. In Chapter 2, pigs were either infected with or vaccinated for PCV2. Fecal samples taken from these pigs were used to assess changes in the microbiome. Overall, the microbiome did not differ at the phylum level, although some organisms were shown to be positively and negatively associated with growth and IgG production. In Chapter 3, experiments were performed to assess the impact of genetic selection for PCV2 resistance on nursery and long-term performance of pigs. Pigs resistant to PCV2 infection had reduced viremia and IgG production. Despite no overall effect on growth performance, the resistant genotypes were found to have lower production costs, especially when infected with PCV2. In Chapter 4, pigs were supplemented with tryptophan to improve postweaning response. Tryptophan improved feed efficiency in experiment 1 and reduced production costs. Tryptophan did not provide the same benefit in experiment 2. Supplementation of tryptophan numerically increased Lactobacillus abundance in experiment 1, but not in experiment 2. In Chapter 5, a series of cell culture experiments were performed to assess the effects of rhamnolipids on IPEC-J2 cells and jejunal explants. Rhamnolipid concentrations exceeding 0.01% were found to be cytotoxic. Lower concentrations were found to be less cytotoxic, but reduced transepithelial resistance in a dose dependent fashion. Secretion of interleukin-8, a marker of inflammation, was observed to be similar to control and LPS samples. Jejunum explants treated with 0.5% rhamnolipid had an IL-8 response higher than controls