The relationship of estradiol-17β concentration in blood serum with the efficiency of oocyte retrieval in cows of the Tagil breed
Abstract
Aspiration of ovarian follicles (OPU) is the major source of oocyte retrieval for in vitro production (IVP) of embryos in cattle. The identification of donors whose OPU-oocytes have the better competence to embryonic development is of interest in terms of increasing the efficiency of oocyte retrieval and in vitro embryos production. The aim of this work was to assess the content of estradiol-17β (E2) in the blood as a predictor of the efficiency of oocyte retrieval and in vitro embryos production technology in lactating donor cows of the Tagil breed. The studies were carried out on cows of the Tagil breed during the middle part of lactation (n = 4). Nine consecutive OPU sessions were carried out on each of the donors with a frequency of twice a week. The concentration of E2, follicle-stimulating hormone (FSH), luteinizing hormone (LH), progesterone and Anti-Mül-lerian hormone (AMH) in blood serum were determined by enzyme immunoassay. A significant effect of the individual features of donor cows on the variability of E2 concentration was revealed, which caused 48.11 % (p<9.1*10-5) variability of this index. The correlations between the concentrations of E2 and LH (Spearman correlation coefficient, rS = -0.71, p<0.001), E2 and AMH (rS = -0.33, p<0.10) were observed. There was a significant (p<0.05) correlation between the level of E2 and the number of blastocysts and blastocyst ratio (rS = -0.37 and -0.38, respectively). In the group with the lower concentration of E2 (M + σ), on average, more blastocysts were produced per OPU session (2.57±0.81 vs 0.17±0.17, p<0.01), which was achieved mainly due to a higher blastocyst ratio (62.1±18.3 vs. 5.3±10.0 %, p<0.01). The correlation between the E2 content in the blood serum at the day of estrus occurrence and at the days of the OPU sessions (rS = 0.86), the concentration of E2 at the day of estrus occurrence can be used to select donor cows of the Tagil breed with the better developmental competence of oocytes in vitro.