Всероссийский научно-исследовательский институт физиологии, биохимии и питания животных – филиал Федерального государственного бюджетного научного учреждения «Федеральный научный центр животноводства – ВИЖ имени академика Л.К. Эрнста»
ABSTRACT. The aim is systematization of literature and authors research data on a number of aspects, including the assessment of the possibility of cows oocyte maturation in vitro in protein-free mediums, the use of different hormonal schemes for in vitro oocytes maturation, maturation of oocytes in vitro using different preparations of follicle stimulating hormone, as well as the possibility of oocyte in vitro maturation medium without hormones. Reproducible and reliable systems for mass production of cattle embryos is currently available in many laboratories around the world. Oocytes cultured in vitro (collected at slaughter with the use of transvaginal ultrasound or by aspiration in live animals) after 24-28 hours of incubation, give the percentage of nuclear maturation of the order 80-90%. In the process of in vitro fertilization by sperm capacitated by heparin, the normal penetration is achieved at a level of 50-60% with frequency of parthenogenetic activation and polyspermy in the range of 10-15% and 5-10%, respectively. Cultivating presumptive zygotes in vitro, one can get up to 40% of blastocysts. On the other hand, the quality of such embryos is inferior in comparison to embryos obtained in vivo and even to zygotes cultured in sheep oviducts, including decreased morphological characteristics and increased sensitivity during freezing. There are also a higher percentages of fetal loss after nonsurgical transplantation of embryos obtained in vitro, which may be due to placental defects. In general, these deficiencies pose a serious obstacle to a more efficient use of in vitro produced embryos in programs for breeding cattle, which assumes the use of modern reproductive technologies, including production of twins, cloning and transgenesis. Therefore, there is a problem in how to improve the viability of in vitro produced embryos and to ensure a satisfactory level of live descendants birth rate. For successful implementation of biotechnology programs, as well as for the purposes of fundamental research on embryos, it is necessary to create optimal culture systems providing a full maturation of oocytes outside the body. To solve this problem, it is advisable to search for the maximal defined media containing no protein components and other ingredients of natural origin which can cause distortion of the experimental results. When using eggs in transgenesis and cloning programs, maturation medium may be saturated with various additional components, but it is necessary to carry out their thorough pre-testing.
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