Pritchett, Elizabeth M.2017-06-142017-06-142016http://udspace.udel.edu/handle/19716/21459Poultry production, particularly broiler production, is an important component of the United States agriculture industry. In 2014, approximately 8.54 billion broilers were produced valuing $32.7 billion dollars (USDA 2014 Poultry Production Summary). Heat stress is an environmental stressor that leads to several welfare concerns such as increased panting and morbidity, increased mortality, decreased feed intake and feed efficiency and, ultimately, economic losses. Several processes are affected as a result of heat stress including the stress response, metabolism, and immunity, among others. The pituitary gland is a neuroendocrine organ that is involved in many of the processes affected by heat stress and it is hypothesized that genes differentially expressed between a heat stress and thermoneutral condition will lead to a better understanding of the bird’s response to heat. In addition to the response to heat, relative tissue expression analysis was used to identify genes (in the thermoneutral condition) that are unique or more abundant in the pituitary gland when compared to all other collected tissues. Validation of transcriptomic data was done using qRT-PCR. Both treatment and thermoneutral birds were euthanized on post-hatch days 21, 22 (1 day heat stress), 26 (acute, 2 hours heat stress), 32 (acute, 4 hours heat stress), and 42 (3 weeks heat stress), whole pituitary glands collected, RNA extracted and RNA-seq stranded libraries prepared. Day 21 birds were naïve to treatment and were used as thermoneutral birds only. Transcriptomic differential expression analysis identified heat-responding genes such as heat shock proteins and indication of the classical stress response at 2 hours of acute heat stress. By four hours, these heat-responding genes and stress responding were no longer differentially regulated. At day 22, heat responding genes were differentially enriched, however, there were fewer genes enriched in the heat stress condition than at the 2 hour time point. By day 42, the transcriptome indicates that the birds have acclimated to the cyclical heat stress and there is no longer a response to heat at the transcriptomic level. Overall, the number of genes enriched in the heat stress condition decreased as the length of exposure to heat increased, and the inverse is true for the differentially expressed genes within the thermoneutral condition (more enrichment of thermoneutral genes as length of heat exposure increased). Relative tissue expression analysis of the thermoneutral birds from days 21, 22, and 42 indicate a shift in overall function of the pituitary gland from neuronal processes at days 21 and 22 to endocrine processes by day 42 indicating maturation of the pituitary gland, possibly as preparation for reproduction.Chickens.Heat -- Physiological effect.RNA.Gene expression.Pituitary gland.Thesis990057236