Transcriptome Analysis of Host Response to Heat Stress in Two Genetically Distinct Chicken Inbred Lines

Heat stress results in reduced productivity, anorexia and mortality in chickens. The objective of the study was to identify genes and signal pathways associated with heat stress in both breast muscle and hypothalamus through RNA-Seq analysis using two highly inbred chicken lines (Leghorn and Fayoumi). At 14d of age, birds were exposed to 38°C with 50% humidity for 4 hours, then 35°C till the conclusion of the experiment. Non-treated individuals were kept at 29.4°C throughout the experiment. For the heat stress group, birds were inoculated at 21d with Newcastle disease virus (NDV) La Sota strain to investigate the effects of heat stress and NDV infection. Physiological response in blood measured at four stages: Pre-heat and at 4h, 7d and 10d post heat treatment (ph), using the i-STAT device suggested differences in response between Fayoumi and Leghorn lines. Breast muscle and hypothalamus were harvested on both 4 hph and 10dph and were used to identify differentially expressed genes (DEG) with a FDR < 0.05. Preliminary analysis identified 10 and 49 DEGs at 4 hph, 205 and 56 DEGs at 10dph in breast muscle; 3 and 4 DEGs at 4hph and 91 and 201 DEGs at 10dph in hypothalamus in Fayoumi and Leghorn, respectively. GO terms such as amino acid metabolic process in heat treated Leghorn breast muscle and response to heat in Fayoumi hypothalamus had been enriched. Further analysis will explore more candidate genes associated with thermal tolerance, which can be used for potential genetic improvement of heat stress in poultry.