The effects of heat stress on the transcriptomics of day28 spleens in Ross 708 and Illinois broilers
Date
2016
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Publisher
University of Delaware
Abstract
Heat stress negatively affects the agricultural industry today. With global temperatures on the rise, evaluating the response of hyperthermia on broiler chickens is a vital application for poultry production. Heat stress can cause immunosuppression and we hypothesize that heat stress suppresses the immune response and negatively affects the splenic function. We predict there will be changes in gene expression seen in the transcriptomic profile comparisons of the D28 spleens from the Ross 708 and Illinois broiler chickens. Broiler eggs were obtained and following hatch, the males were divided into control and heat-stressed groups. The control groups were raised at a constant temperature of 25°C. The heat-stressed groups received eight hours of 39°C cyclic hyperthermia starting at D21 through D28 and maintained at 25°C for the remaining 16 hours of the day. Necropsies were performed approximately three to four hours into the heat cycle on D28 to obtain spleens. RNA extraction was performed and transcriptome libraries were constructed. Morphometric analysis revealed an impact on normalized spleen weights of both lines at D28 and a significant impact at D42. A minimal response was elicited by the spleen and the immune system in all control broiler groups suggesting normal physiological functions. The Ross 708 heat-stressed group highlighted possible occurrence of an intestinal epithelial barrier degradation resulting in the leakage of bacterial toxins into the systemic circulation, and eliciting an innate immune response from the spleen. Several genes products, IL-6, IL-17F, and TGF-β were found to require further investigation to definitively establish a connection with leaky gut syndrome. Overall, heat stress had an impact on the spleen as well as the immune system but, the extent of this effect is not completely understood.