Proteomic profiling of 15-day post-mating preimplantation alpaca embryos reveals estradiol and cortisol pathway signatures

South American camelids (SACs) play an important role in Andean economies, but reproductive inefficiencies, especially early embryonic losses, present significant challenges to herd productivity. This study provides the first proteomic analysis of preimplantation alpaca embryos, offering insights into the molecular mechanisms underlying embryo development and implantation. Using mass spectrometry, we identified 510 proteins in 15-day post-mating (dpm) alpaca embryos. Functional enrichment analysis revealed significant pathways related to cytoskeletal organization, metabolism, embryo elongation, and implantation. Key proteins associated with conceptus elongation, maternal recognition of pregnancy, and steroidogenesis were detected, including keratins (KRT8, KRT18), actin (ACTG1), annexin A2 (ANXA2), and enzymes involved in estradiol and cortisol biosynthesis. The transcripts of VEGFA, Nodal, NGF, and its receptor NTRK1 were detected, emphasizing their roles in early embryo development, and the expression of enzymes linked to estradiol and cortisol synthesis suggests that these hormones play key roles in maternal-fetal communication. Additionally, proteins involved in prostaglandin synthesis, including PTGS2, were identified, supporting their role in conceptus elongation and implantation. This pioneering study provides a foundational dataset for understanding alpaca embryo development at the proteomic level, opening new paths for improving reproductive technologies in SACs. The findings highlight the molecular processes driving alpaca embryogenesis and provide a basis for future research on optimizing assisted reproductive technologies in camelids.