Concentration of progesterone in the blood serum and size of the corpus luteum as criteria for selection of recipient cows for embryo transfer

Abstract

Pregnancy rate is the main factor influencing the productivity and economic efficiency of animal farming. Transfer of bovine cattle embryos is currently one of the most promising methods of overcoming the problem in the reproduction sphere. That is why the objective of our research was to identify progesterone concentration in blood serum and size of the corpus luteum in the cows on the day of embryo transfer in order to improve the strategy of selecting recipient animals, and, as a result, increase the conception rate. All animals admitted to the experiment were divided into three groups based on concentration of progesterone in the blood serum, being <2.5 ng/cm3 in the first, 2.5 to 5.0 ng/cm3 in the second, and >5 ng/cm3 in the third group. Progesterone concentrations in the blood serum and sizes of corpora lutea were determined on the day of embryo transfer (7th day after estrus). The animal was considered pregnant according to a positive result of ultrasound examination. Based on the study results, we concluded that measuring the progesterone content in the blood serum and the size of the corpus luteum are not interchangeable. We found that sizes of corpora lutea did not correlate with concentrations of progesterone in the blood serum of the experimental recipient cows. However, the size of the corpus luteum was of significant predictive value for pregnancy rate. We saw that decrease in its diameter below 15 mm, even against the background of high progesterone concentration, was a negative criterion for selection of the recipient animals. Optimal progesterone concentration in blood serum of the experimental animals was within 2.5–5.0 ng/cm3, leading to the highest pregnancy rate in the groups – 46.7. The hormone parameter outside the indicated range led to a significant decline in the pregnancy rate in the recipient animals. Therefore, when selecting recipient cows prior to transfer, both progesterone concentration in the blood serum and the diameter of the corpus luteum should be taken into account, which should not be beyond the proposed ranges. The data presented and analyzed in the article can help improve the efficiency of transfer of bovine cattle embryos for scientific and industrial purposes.