Amino acids have an important biological role for prevention of cell damage during
cryopreservation. The objective of this study is to determine the effects of cysteine on
postthaw sperm motility, duration of sperm motility, DNA damage, and fertility in the
common carp (Cyprinus carpio). Sperm collected from 10 individuals was cryopreserved in
extenders containing different cysteine concentrations (2.5, 5, 10, and 20 mM). Semen
samples diluted at the ratio of 1:9 by the extenders were subjected to cryopreservation.
After dilution, the semen was aspirated into 0.25-mL straws; the straws were placed on the
tray, frozen in nitrogen vapor, and plunged into liquid nitrogen. DNA damage was evaluated
by comet assay after cryopreservation. Our results indicated that an increase in the
concentration of cysteine caused a significant increase in the motility rate and duration of
sperm in the common carp (C carpio; P < 0.05). Comparing all concentrations of cysteine,
the best concentration of cysteine was 20 mM. Higher postthaw motility (76.00 1.00%)
and fertilization (97.00 1.73%) rates were obtained with the extender at the concentration
of 20 mM. Supplementation of the extender with cysteine was increased the
fertilization and hatching rate and decreased DNA damage. Consequently, cysteine affected
the motility, fertilization, and DNA damage positively, and extenders could be supplemented
with cysteine.