Advances in gamete engineering, embryo technologies, and genetic preservation in domestic carnivores.

Domestic dogs (Canis lupus familiaris) and cats (Felis catus) possess unique reproductive physiologies that have historically limited the development and application of assisted reproductive technologies (ARTs). Major biological constraints include post-ovulatory oocyte maturation and prolonged oviductal residence in the dog, species-specific requirements for sperm capacitation and fertilization, and embryo developmental kinetics that require precise synchronization with the female reproductive tract. Consequently, progress in canine ARTs has been relatively slow, whereas the domestic cat has emerged as a valuable model for biomedical research and a surrogate species for the conservation of endangered felids. Recent advances in gamete preservation, in vitro embryo production, somatic cell nuclear transfer, and genome editing have expanded reproductive biotechnology in domestic carnivores. Among these technologies, sperm cryopreservation remains the most widely applied approach for genetic preservation, although fertility outcomes following the use of cryopreserved semen remain inferior to those achieved with fresh semen. Simplified vitrification strategies using non-permeating disaccharides have shown promising results and may facilitate fieldbased genetic banking and rescue programs. In parallel, improvements in embryo production systems and cloning technologies have enabled the generation of offspring from cryopreserved, cloned, and genome-edited materials. Nevertheless, developmental efficiency remains constrained by species-specific reproductive physiology and the cumulative effects of sublethal cellular damage throughout the reproductive process. Future progress will require a shift from empirical optimization toward mechanism-based approaches focused on developmental competence, improved understanding of canine oocyte biology, standardized cryopreservation protocols, and integration of advanced ARTs into efficient reproductive pipelines for clinical, conservation, and biomedical applications.