Seasonal Differences in Sperm Characteristics and the Level of DNA Fragmentation in Fresh and Cryopreserved Sperm of Saanen Goats

Abstract

Seasonality affects the morphological and functional characteristics of reproductive cells, which makes the natural reproduction of dairy goats possible only in certain seasons. Cryopreservation of sperm, as a part of assisted reproductive technologies, provides their flexibility, which increases the chances of increasing the number of livestock. However, it can cause changes in the morphological and functional characteristics and genetic material of sperm. Therefore, the aim of this study was to determine seasonal changes in the viability, motility, and DNA fragmentation level of native and cryopreserved goat sperm. The experiment was conducted using ejaculates of sexually mature male goats of the Saanen breed, obtained in breeding and nonbreeding seasons. To detect the effect of seasonal differences of seminal plasma on the characteristics of cryopreserved sperm, cells were cryopreserved in ejaculate and following isolation. The results of the study showed that the motility of fresh ejaculate sperm in the breeding season was higher than in the non-breeding season (p ≤ 0.05). Cryopreservation led to a decrease in the number of motile sperm of ejaculate and the selected fraction of sperm in the non-breeding season, and the selected fraction of cells in the breeding season (p ≤ 0.05). When comparing the viability and integrity of sperm DNA, there was a significant decrease in all groups in the non-breeding season compared to the breeding season (p ≤ 0.05). It was found that the DNA fragmentation rate of goat ejaculate sperm in the breeding season after cryopreservation did not change compared to the fresh sample, while that in cryopreserved sperm of the selected fraction of the same season increased (p ≤ 0.05). Cryopreserved spermatozoa of the non-breeding season in the ejaculate and isolated fraction had an increased rate of DNA fragmentation compared to the baseline before cryopreservation. Thus, it can be concluded that the composition of semen liquid varies depending on the breeding season, which affects its cryoprotective properties against spermatozoa during the freezing of ejaculate. Therefore, it is recommended to collect whole ejaculate by freezing in autumn and early winter to improve the effectiveness of artificial insemination using the cryopreserved sperm of male goats of the Saanen breed.