Research note: Untargeted metabolomics to understand the impact of controlled atmosphere stunning and electrical stunning on metabolite profiles of early postmortem breast fillet.

Pre-slaughter stunning influences postmortem muscle metabolism and may affect broiler breast meat quality and processing consistency. Although electrical stunning (ES) and controlled atmosphere stunning (CAS) are commonly used in poultry production, comparative evidence regarding their biochemical impacts during the early postmortem period remains limited. In this study, we utilized an untargeted metabolomics approach to identify metabolite profile alterations in broiler breast muscle following CAS and ES under pilot plant processing conditions. Early postmortem breast fillet samples from Ross 708 broilers stunned using CAS or ES were analyzed using ultra-performance liquid chromatography mass spectrometry (UPLC-MS). Breast fillets (n = 6 per treatment) were collected approximately 30 min postmortem, with early pH measured at 15 min and instrumental color recorded before snap freezing for metabolomics. Meat quality was analyzed using GLM in SAS 9.4, with stunning method as the main effect (P < 0.05). CAS fillets exhibited lower muscle pH than ES fillets (P < 0.001), while color traits were non-significant. Metabolite normalization, statistical analysis, and pathway enrichment were conducted using MetaboAnalyst 6.0. We identified 508 metabolites, of which five differed between CAS and ES at P < 0.05 (uncorrected): methylglyoxal, gluconic acid, (R)-malate, aspartyl-leucine, and 1D-myo-inositol-3-phosphate. All were downregulated in CAS fillets. Pathway analysis showed effects on pyruvate metabolism and the pentose phosphate pathway, with involvement in the TCA cycle, amino acid metabolism, and inositol phosphate signaling. Lower carbonyl stress metabolites and pentose phosphate intermediates in CAS fillets suggest reduced metabolic and oxidative stress, while TCA cycle and proteolysis differences indicate altered postmortem energy use. These findings show stunning methods affect early postmortem metabolism, with CAS inducing fewer stress- and energy-related metabolic changes than ES. Findings are preliminary, given the lack of false discovery rate correction, absence of targeted validation, and potential confounding by sex and body weight. As a practical application, the metabolomic profile of breast tissue helps understand the physiological effects of different stunning methods to enhance meat quality and consumer acceptability and supports optimized stunning protocols.