Antioxidant Glutathione Supplementation in Semen Extenders and its Effect on the Quality of Cryopreserved Bull Sperm: A Meta-Analysis

Glutathione, an organic antioxidant, is believed to suppress the damaging effects caused by reactive oxygen species on post-thaw quality of bull semen. This metaanalysis aimed to evaluate the role and optimal dosage of glutathione in reducing the adverse effects of cryopreservation on post-thaw semen quality of bulls. The analysis used data from 24 articles following various selection processes. The parameters observed were total and progressive sperm motility, acrosomal integrity, sperm viability, morphological abnormalities, plasma membrane integrity, DNA damage, curvilinear velocity, straight linear velocity and fertility. Data were analyzed using the mixed model methodology, with glutathione dosage as the fixed effect and
different studies as the random effect. A significant effect of glutathione was found on post thaw total sperm motility (P<0.05), progressive motility (P<0.05) and plasma membrane integrity (P<0.05). The supplementation of glutathione to semen extenders significantly suppressed the increase in post-thaw sperm abnormalities (P<0.05). Glutathione supplementation in semen extenders had varying effects among different bull breeds (P<0.05). Supplementing glutathione is recommended to improve sperm quality in freezing bull semen. Glutathione supplementation can maintain post-thaw sperm quality with an optimal dosage of 4.49mM.