Seasonal adaptation is associated with systemic metabolic remodelling in heavy pigs: a molecular phenomic approach

Seasonal thermal conditions represent a relevant environmental challenge for finishing pigs, potentially influencing metabolic regulation, physiological homeostasis, and performance outcomes at high slaughter weights. In heavy pigs (approx. 160 kg), environmental conditions may influence systemic metabolic status, with potential implications for physiological robustness and carcass characteristics, which may in turn affect the subsequent seasoning of ham. Molecular phenomic approaches, including plasma metabolomics, provides a valuable tool to characterise integrated physiological responses to environmental variation under field conditions. However, seasonal metabolic variation in heavy pigs has never been characterised using plasma metabolomics. The objective of this study was to characterise seasonal metabolic differences in performance-tested Italian Large White heavy pigs at slaughter using untargeted plasma metabolomics and to evaluate systemic metabolic adjustments associated with pre-slaughter temperature conditions. A total of 193 Italian Large White pigs were included in two seasonal groups: summer, collected across four slaughtering days (n = 87), and winter, collected across three slaughtering days (n = 106), balanced between males and females. Pre-slaughter thermal exposure differed markedly between seasons, with higher 10-day average minimum and maximum temperatures in summer (average min 20.92 °C; max 33.90 °C) compared to winter (average min -3.77 °C; max 3.2 °C). Plasma was collected at slaughter, which was performed in the early morning. Untargeted metabolomics detected 670 metabolites. After quality control, exclusion of xenobiotics, and removal of metabolites with >25% missing values, 580 metabolites were retained for downstream analysis, which included imputation using Multivariate Imputation by Chained Equations. Seasonal comparisons were performed using the Wilcoxon rank-sum test and linear regression. Only metabolites with a Bonferroni-corrected p-value < 0.01 in both analyses were considered significant. Enrichment analysis of significant metabolites was performed using MetaboAnalyst, considering the Relational Database of Metabolomic Pathways and requiring at least three entries per cluster. A total of 193 and 187 metabolites were detected by the Wilcoxon and linear regression analyses respectively, with an overlap of 177 metabolites. Enrichment analysis (RaMP DB) indicated that discriminant plasma metabolites clustered in pathways related to membrane transport, lipid metabolism/signaling, amino acid and branched-chain amino acid catabolism, and nucleotide/pyrimidine metabolism, with additional enrichment for mitochondrial biogenesis (FDR < 0.01). These findings indicate that seasonal temperature variation is associated with coordinated systemic metabolic remodelling in heavy pigs, detectable at slaughter, and identify potential plasma biomarkers of thermal adaptation under field conditions. Research funded by the European Union – NextGenerationEU under the National Recovery and Resilience Plan (PNRR) – FEEDTHEPIG, proposal code P2022FZMJ9 – CUP J53D23018310001 and the European Union’s Horizon Europe research and innovation programme under the grant agreement No. 101059609 (Re-Livestock).