Relationship between Blood Serum Progesterone Levels in Cattle Donors and the Yield and Quality of Embryos

Blood serum progesterone (P4) levels in donor cows and heifers at donor selection, superovulation, insemination and embryo recovery were investigated. Significant differences in P4 levels in the investigated donors during superovulatory oestrus insemination were observed. The cows with low levels of P4 at insemination (5.8 ± 1.7 nmol/l) showed a better yield and quality of embryos (P<0.01) compared to donor cows with high P4 levels at insemination. A negative correlation between P4 levels and superovulatory response (r = -0.70), total recovered embryos (r = -0.47), and transferred embryos (r = 0.44), i.e. lower P4 levels on the day of superovulatury oestrus resulted in an increased yield and quality of embryos. Similarly, a significant difference was observed between donor heifers and cows with high P4 levels on the day of superovulatory oestrus (P<0.01). No significant differences in the yield and quality of embryos (P>0.05) were observed between heifers and cows with low levels of P4 at insemination.