Comparative transcriptome profiling of electrical and controlled atmosphere stunning in finishing pigs

As pork consumption increases, consumer demand for high-quality meat has also increased. To improve pork quality, minimizing stress throughout the slaughter process is essential. Implementation of animal welfare measures can reduce stress, and the stunning stage, which renders animals unconscious, is crucial for ensuring animal welfare, slaughter efficiency, and final meat quality. Previous studies focused on the changes that occur in physiological and physicochemical characteristics following electrical and gas stunning. Using transcriptome analysis, this study aimed to elucidate the changes in gene expression and molecular-level biological responses to electrical and CO2 gas stunning methods. The two stunning methods (electrical stunning, 10 pigs; CO2-controlled atmosphere stunning, 10 pigs) were compared based on transcriptomic changes determined by whole-blood RNA-Seq. Differentially expressed genes were identified for each group (electrical stunning: 67 upregulated and 37 downregulated genes; CO2-controlled atmosphere stunning: 39 upregulated and 17 downregulated genes). Biological mechanisms associated with pig responses to stunning methods were identified through functional annotation. Under electrical stunning conditions, tissue damage responses such as extracellular matrix stability degradation and potential inflammatory reactions were observed. By contrast, under CO2-gas stunning conditions, defense and physiological regulatory mechanisms to buffer oxidative stress were induced, accompanied by immune balance and tissue protection mechanisms. Our study revealed distinct biological mechanisms underlying pig responses to different stunning methods, suggesting that these mechanisms could serve as a cornerstone for assessing slaughter stress, enhancing meat quality, and improving animal welfare.