Kampon KaeoketPanida ChanapiwatPadet TummarukMongkol TechakumphuMahidol University. Faculty of Veterinary Science. Semen Laboratory.2015-06-062017-04-072015-06-062017-04-072015-06-062010Asian Journal of Andrology. Vol.12, No.5 (Sep 2010), 760-7651745-7262https://repository.li.mahidol.ac.th/handle/20.500.14594/1645Cryopreservation is associated with the production of reactive oxygen species, which leads to lipid peroxidation of the sperm membrane and consequently a reduction in sperm motility and decreased fertility potential. The aim of this study was to determine the optimal concentration of L-cysteine needed for cryopreservation of boar semen. Twelve boars provided semen of proven motility and morphology for this study. The semen was divided into four portions in which the lactose-egg yolk (LEY) extender used to resuspend the centrifuged sperm pellet was supplemented with various concentrations of L-cysteine to reach 0 mmol L−1(group I, control), 5 mmol L−1(group II), 10 mmol L−1(group III) and 15 mmol L−1(group IV). Semen suspensions were loaded in straws (0.5 mL) and placed in a controlled-rate freezer. After cryopreservation, frozen semen samples were thawed and investigated for progressive motility, viability using SYBR-14/EthD-1 staining and acrosome integrity using FITC-PNA/EthD-1 staining. There was a significantly higher (P < 0.01) percentage of progressive motility, viability and acrosomal integrity in two L-cysteine-supplemented groups (group II and group III) compared with the control. There was a biphasic effect of L-cysteine, with the highest percentage of progressive motility, viability and acrosomal integrity in group III. In conclusion, 5 or 10 mmol L−1 was the optimum concentration of L-cysteine to be added to the LEY extender for improving the quality of frozen–thawed boar semen.engMahidol Universityantioxidantboar semencryopreservationL-cysteineOpen Access articleArticleAJA, SIMM & SJTU10.1038/aja.2010