Uterine fluid metabolomic profiles across the follicular, luteal, and early pregnancy stages in camelids (Lama glama)

South American camelids exhibit distinctive reproductive traits, including induced ovulation, a short luteal lifespan, and a narrow maternal recognition of pregnancy (MRP) window, which collectively constrain the efficiency of assisted reproductive technologies. During MRP, uterine fluid (UF) provides a dynamic biochemical milieu that supports embryo development and embryo–maternal communication; however, its metabolic composition and regulation remain poorly studied. This study aimed to compare the UF metabolome of llamas across the follicular phase (FP), the GnRH-induced luteal phase (LP-GnRH), and early pregnancy (LP-EP), with the latter two groups analyzed at day 8 post-ovulation, to identify metabolic features associated with endocrine status and embryo presence. Uterine fluid was collected by non-surgical flushing and analyzed using gas chromatography–mass spectrometry, bioinformatics, and statistical tools. Seventy-seven metabolites were identified, largely associated with carbohydrate, lipid, and amino acid metabolism, defining a conserved core UF metabolome. Multivariate analyses revealed differences among reproductive states. The transition from FP to LP-GnRH was characterized by enrichment of β-alanine, pyrimidine, propanoate, and pantothenate/CoA-related pathways, accompanied by differences in the abundance of polyol- and sugar-derived metabolites. The comparison between LP-GnRH and LP-EP revealed differences in metabolites and pathway enrichment involving β-alanine, glycerolipid, and pantothenate/CoA-related metabolism, together with lower abundance of metabolites associated with redox- and carbohydrate-related metabolism and increased glycerol abundance during early pregnancy. Collectively, these findings indicate that reproductive status in llamas is associated with differences in the UF metabolic profile, providing new insights into the reproductive physiology of camelids during early pregnancy and the period of maternal recognition of pregnancy.