The In Vitro Evaluation of Rooster Semen Pellets Frozen with Dimethylacetamide

SIMPLE SUMMARY: Semen cryopreservation remains the most applicable methodology for conserving and transmitting superior genetic backgrounds in poultry species. However, there is wide variability in the results of sperm viability and fertility due to susceptibility to cryodamage. The current study implemented a cryopreservation protocol based on rapid freezing of semen pellets supplemented with various levels of dimethylacetamide (DMA), focusing on in vitro quality, computer-assisted-sperm-analysis (CASA), and anti-freeze-associated gene expression of post-thawed rooster sperm. The current investigation provides novel results regarding the appropriate concentration and molecular mechanism by which DMA could be supplemented to frozen semen pellets and used as a successful protocol for sperm cryopreservation in poultry species. ABSTRACT: Sperm cryopreservation is an effective technique for conserving animal genetic diversity and transmitting superior genetic backgrounds, maintained via a non-invasive sampling and collection of huge quantities of sperm. Nevertheless, cryopreservation in avian species is not commercially viable because of the rooster sperm’s susceptibility to damage. This study aims to estimate the impact of dimethylacetamide (DMA) as a cryoprotectant at different levels (3%, 6%, or 9%) on the post-thawed sperm quality, motility, antioxidant-biomarkers, and the expression of anti-freeze related genes. Semen samples were collected twice a week from twelve roosters aged 40 wk, weighing 3400 ± 70 g, and belonging to the Cairo-B2 chicken strain. Fresh semen samples were rapidly appraised, pooled, diluted with two volumes of a basic extender, and divided equally into three groups. The diluted groups were chilled at −20 °C for 7 min, then gently supplemented with 3, 6, or 9% pre-cooled DMA and equilibrated at 5 °C for a further 10 min. Semen pellets were formed by pipetting drops 7 cm above liquid nitrogen (LN(2)), which were then kept inside cryovials in the LN(2). Thawing was performed 2 months later by taking 3–4 pellets of the frozen semen into a glass tube and warming it in a water bath for 8 s at 60 °C. The results showed that 3% DMA increased the proportion of total motile sperm, progressivity, viability, and plasma membrane integrity (%) compared to the 6% and 9% DMA groups. The lipid peroxidation and antioxidant enzyme activity were improved in the 3% group. At the same time, some anti-freeze-related genes’ (including ras homolog family member A (RHOA), heat shock protein 70 (HSP70), and small nuclear ribonucleoprotein polypeptide A (SNRPA1)) expressions were upregulated within the 3% DMA group relative to other groups. In conclusion, the 3% DMA group maintained higher post-thawed sperm quality than the other tested groups.