The dissertation is devoted to the study of seasonal variability of cryoresistance of Saanen and Alpine bucks spermatozoa (Capra aegagrus hircus) with analyzing the characteristics of their ejaculates: volume, total number of spermatozoa, their motility, morphology, and level of DNA fragmentation; selection of optimal cryoprotective solutions, incorporating considerations for their cytotoxicity; determination of optimal equilibration time with a cryoprotectant; analysis of biochemical parameters of seminal plasma that may affect the characteristics of spermatozoa and determination of the level of heat shock protein gene transcripts; analyzing of embryo development rate, pregnancy and kidding rates.
Solving the task of food security in Ukraine during russian military aggression against Ukraine and during the post–war period is of a high priority. The use of goat products will provide the country with healthy hypoallergenic milk if the technique of dairy goat breeding is adopted throughout the year, as the reproductive characteristics of goats are seasonal. The use of cryopreserved buck semen for in vitro fertilization would increase the productivity of agricultural production and provide the country with the necessary products. Unfortunately, currently, there is little data on the seasonal variability of the semen characteristics of bucks. Thus, seasonal changes in of Saanen and Alpine goat breeds spermatozoa in tropical and Mediterranean climatic zones have been described, but there are no such data in temperate zones, where the alternation of seasons and, accordingly, temperature fluctuations are more pronounced. Fluctuations in seasonal characteristics of buck ejaculates necessitate careful consideration when selecting an appropriate cryopreservation technique, as these variations can impact cryosensitivity. It is worth mentioning that the differences in morphological and functional parameters of spermatozoa of different breeds of goats kept in breeding farms of Ukraine have not been explored, with emphasizing on the climatic conditions and geographical location of our country; the optimal medium for cryopreservation of buck sperm, considering seasonality, has not been developed. Therefore, the aim of the study was to investigate the effect of seasonality on the cryoresistance of spermatozoa of Saanen and Alpine bucks.
We can conclude that the Alpine breed, in comparison with the Saanen breed, was characterized by significantly higher ejaculate volume, total sperm count, cell motility, and viability. Both breeds had significantly higher sperm characteristics in the breeding compared to the non–breeding season.
The survival rate of cryopreserved spermatozoa for both goat breeds was the highest with 10% G and depended on the season of ejaculate collection.
The biochemical characteristics of seminal plasma from buck ejaculates differed depending on the season and correlated with sperm viability after cryopreservation.
The relative level of HSP 90 gene transcripts decreased in the non–breeding season.
The addition of 20% egg yolk to the cryoprotective medium with 10% G allowed to increase of sperm motility from (25.49±2.7)% to (36.50±2.7)% in Saanen bucks and from (31.43±5.75)% to (45.34±5.75)% in Alpine bucks.
After cryopreservation, the level of sperm DNA fragmentation increased by 3–8%. The addition of EY to the cryoprotective medium during the non–breeding season allowed to maintain this indicator at the level of those cryopreserved during the breeding season.
The embryo development rate was significantly higher when oocytes of the breeding season were fertilized with fresh (82.6±3.7)%) and cryopreserved (71.9±9.2)%) spermatozoa of the breeding season, compared to this parameter using cryopreserved spermatozoa of the non–breeding season (57.9±9.7)%) (p˂0.05). After the transfer of embryos to the uterine cavity, the pregnancy and kidding rates did not depend on the season of fresh or cryopreserved sperm.
