Morphological Characteristics for Oocyte-Cumulus Complexes of Bos taurus and Bos indicus Cattle Used for a Variety of Purposes

Abstract

The technology for the intravital in vitro bovine embryo production utilizes the qualitative and quantitative criteria for the initial population of the viable oocytes to determine the successful development of blastocysts suitable for native embryo transfer or cryopreservation. Therefore, a study of the reproductive potential of Bos taurus and Bos indicus (zebu cattle) cows used for a variety of purposes with the method for oocyte quality and quantity assessment is of scientific and practical interests. The objective of the work is to perform a comparative analysis of the Russian and Brazilian cattle in the yield of the oocyte-cumulus complexes (OCC) and their morphological characteristics for the dairy and beef cattle within populations. The cows were grouped into the Aberdeen-Angus (n = 82), Black-and-White (n = 62), Nelore (n = 149), and Gir (n = 63) cattle breed categories. The oocyte-cumulus complexes obtained by transvaginal puncture of follicles served as the survey materials. The OCC quality was assessed with the use of the following parameters: the presence of OCC layers, the OCC quality, the oocyte size, the homogeneity scale, the ooplasm color, and the turgor pressure. The numbers of the viable OCC of their total quantity comprise 67.2, 42, 83.9, and 71.4% for the Aberdeen-Angus, Black-and-White, Nelore, and Gir cattle breed categories, respectively. It has been concluded that the Bos indicus (zebu-like) cattle have the potential to be used in the technology for in vitro embryo production, since they are more than twice as likely to dominate over the Bos taurus cattle in the oocyte yield.