Effects of pyrroloquinoline quinone (PQQ) on ram sperm quality and fertility potential during cooled storage.

Ram spermatozoa are highly susceptible to cold-induced oxidative damage due to the abundance of polyunsaturated fatty acids (PUFAs) in their plasma membrane, which ultimately compromises fertilizing capacity. Adding antioxidants to semen extenders is a known strategy to protect sperm quality during cooling. This study evaluated the effects of different concentrations of pyrroloquinoline quinone (PQQ) in ram semen extender during chilled storage at 4°C. Semen samples were collected, diluted, and split into five groups: control (nothing added) and four groups with 10, 100, 1000, or 10000 nM PQQ. They were stored at 4°C for 48 h and checked for total motility (TM), progressive motility (PM), viability, membrane integrity (HOST), lipid peroxidation (MDA), and mitochondrial membrane potential (MMP) at 0, 24, and 48 h. In addition, fixed-time cervical artificial insemination (FTAI) was performed using semen stored for 24 h in 800 ewes. At 0 h, there were no differences among groups (P > 0.05). At 24 and 48 h, the PQQ100 group had higher TM, PM, viability, HOST, and MMP, and lower MDA than the other groups (P ≤ 0.05). Pregnancy, parturition, and lambing rates were also better (P ≤ 0.05) in the PQQ100 group (55.0%, 55.0%, and 57.0%) compared with the control group (29.0%, 27.5%, and 28.5%). Therefore, adding 100 nM PQQ to ram semen cooling extender appears to preserve sperm quality and fertility during storage at 4°C.