Bovine uterine fluid lipidome parallels embryo and conceptus developmental milestones†

An optimal uterine luminal fluid (ULF) microenvironment is essential for successful pregnancy establishment and progression. Despite this, the specific factors influencing early embryo and conceptus (embryo and extra-embryonic structures) survival remain poorly understood. Lipid moieties dominate the ULF metabolome and are thought to play crucial roles in embryo and conceptus development. As such, we aimed to comprehensively profile the bovine ULF lipidome at four key times of the estrous cycle-Days 0, 7, 10, and 14. Our analysis identified 80 distinct lipids, which were categorized into 29 metabolic pathways. We observed significant (P ≤ 0.05) temporal variation in lipid abundance, with certain lipids uniquely present on specific days. Notably, carnitine derivatives exhibited pronounced changes in abundance throughout the cycle. These findings highlight the dynamic nature of ULF lipid composition and its potential influence on early reproductive events. We also discuss the implications of these results for enhancing both in vivo and in vitro embryo development.