Effects of cysteine supplementation on the quality of cryopreserved sperm of South American silver catfish

The cryopreservation promotes cellular damage that could compromise sperm quality in terms of motility and fertility rates, which may be caused by oxidative stress. Thus, the aim of this study was to assess the effects of cysteine addition on post-thaw sperm quality, DNA damage and indices of oxidative stress of the South American silver catfish (Rhamdia quelen) sperm, compared with the cryoprotectant solution without cysteine addition. Sperm collected from five males were cryopreserved in cryoprotectant solution (fructose 50 g/L, powdered milk 50 g/L and methanol 100 ml/L) containing different cysteine concentrations (0, 2.5, 5, 10 and 20 mM). After thawing, the following were measured: sperm motility, morphology, sperm viability, DNA damage, lipid peroxidation, concentration of carbonyl and sulfhydryl groups and the activity of SOD, CAT, GST and GPx enzymes. The lowest sperm motility was determined for semen cryopreserved with addition of 20 mM of cysteine. The control group had the lowest DNA damage and lipid peroxidation. The findings of this study show that cysteine addition had no positive effect on evaluated parameters. Therefore, the concentrations tested are not recommended for the supplementation of cryoprotectant solution for semen of R. quelen.