Effect of Semen on the Embryo Productivity of Donor Cows and the Development of Transplant Calves

: In animal husbandry, more heifers are required for the expanded reproduction of the herd or milk, and more bulls are needed to obtain meat. One of the effective ways to artificially regulate the secondary (at birth) sex ratio is the technology of sexed semen. In this connection, the purpose of this study was to study the effect of sexed and native semen on the embryonic productivity of donor cows, the survival rate of embryos in recipient cows, and the development of transplant calves. The studies were carried out on Simmental cows in the period from 2017 to 2019 in the Galitskoe LLP and Pobeda LLP in the Pavlodar region (Republic of Kazakhstan). It was found that 80 (78.4%) of 102 embryos were suitable for transplantation in cows fertilized with native sperm and 31 of 51 embryos (60.8%) in cows inseminated with sexed sperm. At the same time, embryos at the stage of compact morula and early blastocyst prevailed in both groups of cows. Later, at the time of embryo transplantation to recipient cows, the survival rate was 59.5% for two-sex and 58.3% for single-sex transplants. During the analysis of postnatal development of different-sex transplant calves, it was found that although they were characterized by different growth dynamics depending on sex, they generally exceeded the calves of the control group in this parameter. The detected differences in superovulation and embryo productivity of cows of the Simmental breed show that the individual characteristics of donor cows are decisive regardless of which sperm (native or sexed) was used for artificial insemination. At the same time, in all cases, donor cows fertilized with native semen were distinguished by the best embryo productivity, although the differences with cows inseminated with sexed sperm were not significant .