Changes in Porcine Muscle Gene Expression: Influence of Stunning Gases and Postmortem Time Course

Stunning pigs with inert gases has reportedly led to differences in pork quality. In the present study, we investigated how different inert gas atmospheres affect the muscle transcriptome, aiming to identify changes in RNA expression that could explain potential differences in meat quality. Therefore, total RNA was extracted from 120 slaughter-weight pigs, which were stunned pairwise either with argon, a nitrogen-argon mixture, or carbon dioxide. To control for potential slaughter day effects, 2 CO2 control groups were included, resulting in 30 animals per stunning condition. Muscle samples from the M. longissimus thoracis et lumborum were collected at 45 min and 36 h postmortem, respectively. For each stunning method and time point, sequencing was performed on 3 pooled samples, each comprising 10 animals. The comparison of the muscle transcriptomes revealed 112 genes to be differentially expressed (absolute Log2Foldchange >1, P adjusted < 0.01) between 45 min and 36 h postmortem across all gas comparisons. Gene set enrichment analysis revealed them to be involved in pathways like the cytoskeleton in muscle cells and protein digestion and absorption. Out of these genes, 24, including Protein phosphatase-1 regulatory subunit 3A (PPP1R3A), were found to be upregulated at 36 h postmortem. When comparing the effects of the different stunning gases, a total of 26 genes were differentially expressed (absolute Log2Foldchange >1, P adjusted < 0.05), although this was not significant in all comparisons. This study is the first to characterize the transcriptome of the M. longissimus thoracis et lumborum in pigs depending on the gas used for stunning. Moreover, we were able to identify distinct transcriptomic profiles at different postmortem time points, providing new insights into the transcriptomic changes occurring in porcine muscle tissue after slaughter.