Biochemical predictors of pregnancy in cattle: Enhancing recipient selection for embryo transfer efficiency

This study assessed potential biochemical markers to improve the selection of recipient cows in embryo transfer (ET). Previous efforts have focused primarily on the selection of donor cows, along with oocyte quality; however, the physiological status of recipient cows is also important for ensuring successful pregnancies. Blood samples were collected from 30 recipient cows, followed by estrus synchronization. Using their plasmas, their enzymes, metabolites, electrolytes, and related physiological indicators were evaluated. Correlation analyses revealed that the levels of alanine aminotransferase (ALT) and inorganic phosphate (IP) were significantly correlated with pregnancy outcomes. The pregnancy rates of recipient cows with ALT levels ≥23.5 U/L (60.00 ± 24.49 %) significantly exceeded those of recipient cows with lower levels (12.00 ± 6.63 %), suggesting that ALT may be a suitable predictor of fertility potential even within the normal range. Conversely, recipient cows with IP levels >7.05 mg/dL did not reach pregnancy, whereas those with IP ≤ 7.05 mg/dL had significantly higher pregnancy rates (42.86 ± 13.73 %). The predictive accuracies of ALT and IP for pregnancy outcomes were 83.33 % and 73.33 %, respectively. These findings suggest that the ALT and IP levels may serve as practical physiological indicators for the selection of recipient cows for ET. In addition, incorporating biochemical profiling into recipient selection may enhance the efficiency and predictability of cattle ET. Further studies considering larger herds are needed to validate the findings and optimize the threshold values. Overall, this study provides new insights for improving reproductive performance and advancing genetic gain during cattle breeding.