Effects of sperm concentration on the quality of cryopreserved sperm in Yangtze sturgeon (Acipenser dabryanus)

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The Yangtze sturgeon (Acipenser dabryanus) is extinct in the wild; however, artificial propagation in captivity under fully controlled conditions has been successful. Sperm cryopreservation is an effective method for germplasm conservation and aquaculture. Sperm concentration affects the quality of cryopreserved spermatozoa. Thus, in this study, we optimized the concentration (0.25 × 109, 0.5 × 109, 1.0 × 109, and 2.0 × 109 spermatozoa [spz]/mL) for Yangtze sturgeon sperm cryopreservation in a 0.5 mL plastic straw. The greatest value for the kinetic parameters was achieved when sperm were cryopreserved at 0.5 × 109 spz/mL. In comparison to other concentrations, there was a notable increase in both acrosomal and plasma membrane integrity when sperm was cryopreserved at a concentration of 0.5 × 109 spz/mL. No significant difference of superoxide dismutase and glutathione peroxidase enzyme activity was present in post-thaw sperm, except in sperm cryopreserved at a concentration of 2.0 × 109 spz/mL. Catalase activity was significantly higher in post-thaw sperm at a concentration of 0.5 × 109 spz/mL than at other concentrations. Excluding sperm cryopreserved at 2.0 × 109 spz/mL, the fertilization rate of cryopreserved sperm was not significantly different among the different concentrations. This concentration optimization improves cryopreserved sperm quality and standardizes sperm cryopreservation procedures for the Yangtze sturgeon. These findings are especially beneficial for the establishment of a sperm cryobank.