381 Investigation of heat stress on differential gene expression in tolerant and susceptible pigs
Abstract Heat stress adversely affects pig growth and reproduction performance by reducing feed intake, body weight gain, farrowing rate, and litter size. Heat tolerance is an important trait in pigs, allowing them to mitigate the negative effects of heat stress on their physiological activities. Yet, genetic variation and signaling pathways associated with the biological processes of pigs tolerant to heat stress are currently not fully understood. This study aimed at identifying differentially expressed (DE) mRNAs of pigs under different heat-stress environments using whole transcriptomic RNA-seq analyses. RNA was isolated from blood samples of boars (n = 12) collected at two time points (late winter and middle summer) and labeled as pre-stress when subjected to no heat-stress, and stress when subjected to heat stress for 2 months. Semen parameters, including sperm count, motility, normal morphology, droplets, and rejected ejaculate rate, were measured for boar classification into either tolerant or susceptible to the heat stress. Genes displayed different expression levels between susceptible and tolerant pigs under pre-stress, and stress period respectively. A total of 692 DE genes (654 down-regulated, 38 up-regulated) were found in susceptible pigs compared to tolerant pigs during the pre-stress period. A total of 724 DE genes (622 down-regulated, 62 up-regulated) were found in susceptible pigs compared to tolerant pigs during the heat stress period. Heat stress showed greater effects in significant transcript expression (FDR < 0.05) among susceptible pigs than tolerant pigs with 88 DE genes (51 down-regulated, 37 up-regulated) and 5 DE genes (1 down-regulated, 4 up-regulated), respectively. This study contributed to the expression profiles of transcripts and the exploration of novel genes in pigs responding to heat stress.