Exploring the characters of sperm lipid peroxidation, enzymatic antioxidant activity, and spermatozoa zona binding capacity with aging in dogs.

This study aimed to assess differences in fresh semen quality between mature and senile dogs, focusing on oxidative stress markers, including spermatozoa lipid peroxidation and enzymatic antioxidant activity. Furthermore, the ability of frozen-thawed spermatozoa from these age groups to bind to the zona pellucida was investigated. Forty clinically healthy dogs were categorized into two groups: mature (3 ± 0.2 years; n = 20) and senile (10 ± 0.2 years; n = 20). A total of 107 semen samples (2-3 ejaculates per dog) were analyzed for motilities and kinetic parameters, sperm concentration, total sperm count (TSC), acrosome and membrane integrity, morphological defects, DNA fragmentation, lipid peroxidation, and the enzymatic activities of superoxide dismutase, catalase, and glutathione peroxidase in spermatozoa and seminal plasma. A zona-binding assay was performed using frozen-thawed semen from mature (n = 10) and senile (n = 10) dogs. Mature dogs exhibited significantly higher total motility, sperm concentration, TSC, membrane integrity, and zona binding capacity compared to senile dogs (P < 0.05). Conversely, senile dogs had significantly higher proportions of proximal cytoplasmic droplets and tail defects (P < 0.05). However, lipid peroxidation, enzymatic antioxidant activities, and acrosome integrity did not differ significantly between the groups (P > 0.05). In conclusion, the observed decline in fresh semen quality with age in dogs does not appear to be associated with increased susceptibility to oxidative stress. Furthermore, frozen-thawed spermatozoa from mature dogs exhibited superior zona binding capacity, likely due to a greater proportion of progressively motile sperm.