Browsing by Subject "Biological sciences"
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Item Evaluation of dietary factors limiting caloric and nutritional efficiency in pork production(2021-08) Hung, Yuan-TaiSwine nutrition research goes beyond diet formulation and feeding pigs. When considering a systems approach, swine nutrition research is indispensable to improve food security, animal well-being, animal health, sustainability, and the environmental impact of production systems. The One Health concept has emerged to ensure optimal health outcomes toward animals, humans, and the environment. This can be achieved in the swine industry by optimizing nutrient utilization of pigs and removing antimicrobial growth promoters (AGPs) from diets. With the aim to improve pig production performance, four studies were conducted to investigate dietary factors that limit caloric and nutritional efficiency of pigs. Research in chapters 2 and 3 indicated that lipid peroxidation has detrimental effects on animal health and growth performance of swine and poultry fed iso-caloric diets, whereas adding antioxidants enhance lipid stability preventing further lipid peroxidation of supplemental lipids, reducing incidence of oxidative stress in pigs. Research in chapter 4 revealed that diets with increased viscosity induced by dietary fiber changed intestinal morphology and digestive enzyme activities with decreased energy and nutrient digestibility in pigs. Research in chapter 5 characterized growth-related responses in the intestine of pigs fed AGPs, shedding light on the potential mechanisms of growth-promoting effects of antimicrobials that could guide the discovery of AGP alternatives. In this dissertation, a novel approach combining swine nutrition research and digestive physiology was adopted to pinpoint dietary factors limiting nutrient utilization and growth in pigs. The main findings from this research on feeding lipids, dietary fiber, and AGPs will help develop sustainable feeding programs for pigs and achieve One Health.Item Molecular phylogenetics of the New World blackbirds (Icteridae)(2012-12) Powell, Alexis Frederick Leo AlveyThe New World blackbirds (Icteridae) are among the best known songbirds, both through exemplar species, such as the Red-winged Blackbird (Agelaius phoeniceus), and collectively, as a model clade in studies of morphological, ecological, and behavioral trait evolution. Knowledge of phylogeny is a prerequisite for comparative studies and the basis for systematic classification, yet there has been no comprehensive analysis of blackbird phylogeny. In Chapter 1, I present the phylogeny of the grackles (Quiscalus spp.) inferred from cytochrome b and ND2 gene sequences. A primary concern was determining the relationships of the extinct Slender-billed Grackle (Q. palustris) and Q. nicaraguensis, which is unusual among grackles for its restricted geographic range. I found the Slender-billed Grackle to be most closely related to one of two major haplotype clades of Q. mexicanus, the other being sister to Q. major. Q. nicaraguensis appears sister to Q. lugubris. I also found that Q. mexicanus, niger, and lugubris contain deeply-divergent lineages. In Chapter 2, I present a method for partitioning whole mitochondrial genome sequences to optimize model-fitting during phylogenetic analyses. Because standards for rigorous phylogenetic analyses of mitogenomes were lacking, developing such a method was a prerequisite for analyzing the mitogenomes of a clade of South American endemic blackbirds. I found that the most useful categories for partitioning were codon position, RNA secondary structure pairing, and the coding/noncoding distinction, and that a scheme with nine data groups outperformed all of the more complex alternatives (up to 44 data groups) that I tested. In Chapter 3, I present the first comprehensive species-level phylogeny of the Icteridae. By using mitochondrial gene sequences from all ~108 currently-recognized species, together with strategic sampling of 4 nuclear loci and whole mitochondrial genomes at the generic level, I was able to resolve most relationships with high confidence. The best-resolved phylogeny is consistent with strongly-supported results of past studies, but it also contains many novel robustly-resolved inferences of relationship, including some unexpected placements of taxa that had not been included in previous molecular phylogenies, resolution of the relationships among major subclades within Icteridae. I suggest taxonomic revisions based on those results.