Animal Molecular Breeding 2024, Vol.14, No.3, 217-227 http://animalscipublisher.com/index.php/amb 219 Table 1 MicroRNAs characterized in oocytes of rFSH and rFSH-rLH treatment protocols (Adopted from Konstantinidou et al., 2023) No. of microRNAs r-hFSH r-hFSH + r-hLH 1 hsa-miR-548c hsa-miR-548c 2 hsa-miR-222 hsa-miR-222 3 hsa-miR-484 hsa-miR-484 4 hsa-miR-539 hsa-miR-486-3p 5 hsa-miR-636 hsa-miR-17 6 hsa-miR-17 mmu-miR-140 7 hsa-miR-130a hsa-miR-520d-5p 8 mmu-miR-140 hsa-miR-518d 9 hsa-miR-520b hsa-miR-548a 10 hsa-let-7b hsa-miR-627 11 hsa-miR-106a - 12 hsa-miR-520d-5p - 13 hsa-miR-518d - 14 hsa-miR-548a - 15 hsa-miR-628-5p - 16 hsa-miR-525-3p - 17 hsa-miR-627 - 3.3 Embryo culture and developmental stages The culture and development of embryos are crucial for successful embryo transfer. Advances in cell culture media have led to improved outcomes in embryo development. For example, the use of optimized in vitro maturation (IVM) protocols has resulted in high maturation and fertilization rates, with significant blastocyst development (Junk and Yeap, 2012). In lions, IVM and intracytoplasmic sperm injection (ICSI) have been successfully performed, resulting in the development of blastocysts, although the developmental speed was slower compared to domestic cats (Fernandez-Gonzalez et al., 2015). Additionally, studies have shown that blastocyst stage transfers result in higher live birth rates compared to cleavage stage transfers, suggesting that extending embryo culture to the blastocyst stage could improve outcomes in feline breeding programs (Glujovsky et al., 2016). By integrating these techniques, feline breeding programs can enhance the efficiency and success rates of embryo transfer, ultimately contributing to the conservation and propagation of endangered feline species. 4 Embryo Transfer Protocols 4.1 Selection of recipient queens The selection of recipient queens is a critical step in optimizing embryo transfer (ET) techniques in feline breeding programs. Recipient queens should be in good health, have a proven reproductive history, and be free from any reproductive disorders. The body condition score (BCS) is an essential factor, as it influences the success of the ET program. Proper nutrition and health management are crucial to ensure that the recipient queens are in optimal condition to receive and support the transferred embryos (Sala et al., 2020). 4.2 Timing and synchronization of donor and recipient Synchronization of the estrous cycles of donor and recipient queens is vital for the success of ET. Fixed-time embryo transfer (FTET) protocols, which eliminate the need for estrus detection, have been shown to improve synchronization and increase the efficiency of ET programs. These protocols often involve the use of gonadotrophin-releasing hormone (GnRH), prostaglandin F2α (PGF2α), and progesterone-releasing devices to control follicular wave emergence and ovulation (Baruselli et al., 2010; Baruselli et al., 2011). The timing of hormone administration is crucial to ensure that the recipient queen’s uterine environment is synchronized with the developmental stage of the transferred embryos (Sala et al., 2020). 4.3 Embryo transfer procedures The ET procedure involves the careful handling and transfer of embryos into the recipient queen's uterus.
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