FORECASTING THE EMBRYO PRODUCTIVITY OF DONOR COWS ON THE BASIS OF ECHOGRAPHIC CHARACTERISTICS OF THE OVARIES

The main problem restricting the wide use of reproductive biotechnology in animal husbandry is insufficiently developed methods for selection of donor cows for embryo transfer. The objective reason is the variability of the ovarian response to gonadotropins injections. Until now, there is no reliable information about possibility of forecasting the embryo productivity of donor cows before gonadotropin stimulation, which affects substantively the economic feasibility of embryo transfer as a method of accelerated cattle reproduction. We have applied the post-pressing analysis of ovaries echograms for forecasting the embryo productivity of donor cows on the basis of comparisons of quantitative and qualitative indicators of ovaries after induced superovulation and its’ echographic characteristics. We carried out morphofunctional study of ovaries in donor cows (n = 30) on day 10 of estrous cycle, before artificial insemination (estrus) and on day 7 of the inducted estrous cycle, immediately before the extraction of embryos using data on post-pressing ovarian morphometry. Animals were divided into three groups (I, II и III, n = 10 for each group) with yellow body length of 2.5 cm, 1.5-2.5 cm and 1.5 cm, respectively. Echographic visualization of the ovaries was performed using endorectal ultrasonography. Polyovulatory response of ovaries was induced with FSHsuper (Russia) injected eight times, with 12 h interval, at decreasing doses. The embryos were recovered on day 7 after artificial insemination. Optimal criteria for predicting the polyovulatory response of ovaries and the quantity of embryos were determined on the basis of the ovarian morphometry. Statistically significant differences with the control were assessed by the Student’s t-test. It was found that the average areas of the ovaries on the echograms were 7.9±0.94, 5.7±0.78 and 3.5±0.06 cm2 for group I, group II and group III, respectively. The area of the yellow body in group I averaged 4.5±1.21 cm2, was 2.08 cm2 higher (P  0.05) than in group II, and exceeded the corresponding parameter in group III by 3.43 cm2 (P  0.05). A comparative evaluation of the ratio of the yellow body areas to the ovaries area of each animal and on average along the groups showed that in group I with the ratio of 57.1±3.01 % the number of yellow bodies was 11.6±1.26 and the average yield of the embryos was 9.3±1.23 per animal. In group II with the ratio of the areas of yellow bodies and ovaries of 42.1±2.9 % the number of yellow bodies before embryos recovery was 5.7±1.24, and 4.6±1.01 embryos were recovered per procedure. The lowest embryo recovery (less than one embryo per procedure) was observed in group III with the relative area of yellow bodies of 30.2±2.56 % and the average number of the yellow bodies of 1.8±0.18. Comparison of the size of the yellow bodies before the induction of polyovulation and data characterizing the efficiency of induction of superovulation and recovery of embryos showed that in animals with a ratio of the areas of the yellow body and ovary more than 50 %, high response can be obtained resulting in 11.6±1.26 yellow bodies and 9.3±1.23 embryos per extraction.