Transcriptome analysis reveals that constant heat stress modifies the metabolism and structure of the porcine longissimus dorsi skeletal muscle.

Exposure to high ambient temperatures is detrimental to pig rearing and porcine meat quality. Deep molecular sequencing allows for genomic characterization of porcine skeletal muscles and helps understand how the genomic landscape may impact meat quality. To this end, we performed mRNA-seq to molecularly dissect the impact of heat stress on porcine skeletal muscles, longissimus dorsi. Sixteen castrated, male DLY pigs [which are crossbreeds between Duroc (D) boars and Landrace (L) × Yorkshire (Y) sows, 79.0 ± 1.5 kg BW] were evenly split into two groups that were subjected to either control (CON) (22 °C; 55 % humidity) or constant heat stress (H30; 30 °C; 55 % humidity) conditions for 21 days. Seventy-eight genes were found to be differentially expressed, of which 37 were up-regulated and 41 were down-regulated owing to constant heat stress. We predicted 5247 unknown genes and 6108 novel transcribed units attributed to alternative splicing (AS) events in the skeletal muscle. Furthermore, 30,761 and 31,360 AS events were observed in the CON and H30 RNA-seq libraries, respectively. The differentially expressed genes in the porcine skeletal muscles were involved in glycolysis, lactate metabolism, lipid metabolism, cellular defense, and stress responses. Additionally, the expression levels of these genes were associated with variations in meat quality between the CON and H30 groups, indicating that heat stress modulated genes crucial to skeletal muscle development and metabolism. Our transcriptomic analysis provides valuable information for understanding the molecular mechanisms governing porcine skeletal muscle development. Such insights may lead to innovative strategies to improve meat quality of pigs under heat stress.