RESUMEN
This study aimed to investigate maternal serum levels of some angiogenic factors and certain proteins in dairy cattle for (1) early prediction of unsuccessful fertilization and (2) early detection of possible pregnancy failures (early EM) after positive insemination Serum samples were collected from the same cattle at three distinct time points: 30 days before artificial insemination (B-AI), on the day of artificial insemination (AI), and 30 days after artificial insemination (A-AI). As a result of the pregnancy examination, the cows were divided into two main groups according to whether they were pregnant. The results showed that leucyl/cystinyl aminopeptidase (LNPEP) concentration was significantly decreased B-AI and Secreted frizzled-related proteins (SFRP-3), Vascular Endothelial Growth Factor (VEGF) and LNPEP levels were significantly decreased on day of AI, while PRL level was increased, and these data have prognostic significance as early indicator of the risk of potentially failed pregnancy. Additionally, a significant decrease in LNPEP, SFRP3, and VEGF levels, along with an increase in PRL levels was also observed in A-AI. These results suggest that these biomarkers can be used as a screening test to monitor the course of pregnancy. There were no significant differences in serum levels of Insulin-Like Growth Factor 2 (IGF-2), Tissue inhibitors of metalloproteinases (TIMP-1), angiopoietin (ANG), Endoglin (ENG), Fibroblast growth factor (FGF), Inhibine-A (INH-A) and Transforming growth factors-ß1 (TGF-ß1) between the evaluated periods neither unsuccessful nor the successful pregnancy groups. This is the first study reporting that the maternal serum levels of LNPEP, SFRP3, VEGF, and PRL have important roles in pregnancy success and may indicate whether insemination outcome will be successful B-AI and predict the risk of unsuccessful pregnancy after AI in dairy cattle. The increase in such studies will allow the development of more specific, practical, and applicable markers.