Degree Type

Dissertation

Date of Award

2016

Degree Name

Doctor of Philosophy

Department

Animal Science

Major

Genetics

First Advisor

Susan J. Lamont

Abstract

Climate change is expected to increase the average global temperature and negatively impact the food supply. Increasing population and economies increase demand for dietary animal protein. Heat stress in chicken decreases production and increases disease susceptibility. Understanding the genetic control of response to heat in chickens could enable breeding more climate-adaptable chickens that are heat and/or disease resistant. Therefore, we characterized the response to heat and/or immune stimulation using unique genetic lines as a discovery platform using population, tissue, and isolated cell population studies. At the population level, a highly advanced intercross line originating from broiler (heat susceptible) and Fayoumi (heat resistant) were exposed to heat stress; body temperature, growth, digestibility, and blood chemistry components were measured. Most traits were estimated to have low to moderate heritabilities. Using the 600K SNP array genotypes, 96 QTL were identified along with positional candidate genes. In another study, broiler and Fayoumi chickens were exposed to heat and/or the immune stimulus of lipopolysaccharide (LPS). Spleen transcriptional profiles were determined using RNA-sequencing technology. Differentially expressed genes were identified in all treatment contrasts, with the largest effect observed in response to LPS+heat in both breeds. Ingenuity pathway analysis revealed unique pathways in response to heat such as Remodeling of Epithelial Adherens Junctions. In response to treatment with LPS, many immune-related pathways were identified, such as Granulocyte Adhesion and Diapedesis. In response to LPS+heat the pathways were mostly immune-related, including Role of Macrophages, Fibroblasts and Endothelial Cells in Rheumatoid Arthritis. We performed an in vitro study using cells collected from Fayoumi (disease resistant) and Leghorn (disease susceptible). Bone marrow derived dendritic cells were stimulated with heat and/or LPS and functionally characterized. Fayoumi cells produced more nitric oxide, phagocytosed more, and had higher MHCII surface expression compared to the Leghorn. Collectively, this research contributes essential knowledge that there is a genetic component to response to heat and/or immune stimulation in chickens, a foundation for further investigation and potential avenues for population improvement.

Copyright Owner

Angelica Grace Van Goor

Language

en

File Format

application/pdf

File Size

207 pages

Included in

Genetics Commons

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