Untargeted Metabolomic Differences Between Colostrum and Mature Milk in Lactating Sows: Biological Significance and Implications

This study investigated the temporal metabolic differences between sow colostrum and mature milk using an untargeted metabolomics approach. Nine multiparous Camborough sows were longitudinally sampled for colostrum and mature milk collection. Proximate analysis demonstrated that protein content was significantly greater in colostrum than in mature milk (p < 0.05). Untargeted metabolomic profiling successfully putatively annotated 3906 metabolites, with 560 significantly increased and 1083 decreased in colostrum compared to mature milk. Multivariate statistical analyses, including PCA and OPLS-DA, confirmed distinct metabolic separation between the two lactation stages. Furthermore, pathway enrichment and Differential Abundance score analyses revealed that diverse lipid metabolism pathways, fat digestion and absorption, thermogenesis, and glycerolipid synthesis were significantly elevated in mature milk. Physicochemical evaluation indicated that mature-milk-enriched metabolites exhibited significantly greater molecular weights and Log P values, reflecting enhanced structural complexity and lipophilicity. These comprehensive differences suggest that mature milk features higher-molecular-weight and lipophilic metabolites aligned with changing nutritional requirements during later lactation, whereas colostrum is enriched with simpler fractions characteristic of the early postpartum stage. Collectively, this study establishes a comprehensive comparative metabolic baseline of sow milk, providing a robust framework for understanding maternal metabolite dynamics with potential application for optimizing sow nutrition and milk quality.