Transcriptome Analysis of Genetic Resistance to Heat Stress in Two Genetically Distinct Chicken Inbred Lines

Heat stress results in reduced productivity, anorexia and mortality in both broilers and laying chickens. Genetics plays a significant role in the physiological response to heat stress. The objective of this study was to identify genes and pathways associated with heat stress by RNA-seq analysis using two genetically distinct highly inbred chicken lines (Fayoumi, resistant, and Leghorn, susceptible, to viral infection). At 14 days of age, the heat stress group was treated at 95 F with 60% relative humidity until the end of experiment, while the control group followed regular room temperature (80 F). Individual body temperature and physiological blood parameters measured using the iSTAT were recorded at four stages: Pre-heat (Day 13), Acute Heat (AH, 4 hours post heat treatment), Chronic heat 1 (CH1, 7 days post heat treatment) and Chronic heat 2 (CH2, 10 days post heat treatment). Changes in body temperature from Pre-heat to CH2 were significantly different between heat treated and control groups in both genetic lines. Fayoumi demonstrated more physiological differences that were statistically significant between treatment groups than Leghorn, especially from Pre-heat to CH1 (12 vs. 4 out of 13). Livers of Leghorn and Fayoumi birds from both heat treatment and control groups were harvested at all stages. Sixteen cDNA libraries at CH2 stage were prepared and sequenced. The on-going RNA-seq data analysis will identify genes and pathways associated with heat stress. This study will provide an important first step for further characterization of genetic resistance to heat stress in the chicken.