The effect of dietary grape pomace supplementation on epididymal sperm quality and testicular antioxidant ability in ram lambs.

Wine grape pomace (WGP) contains a rich source of polyphenols that can act as powerful antioxidants. The objective of this study was to investigate the effect of dietary WGP supplementation on antioxidative activity and epididymal sperm quality in rams. The rams were raised either under free-range or pen conditions, and the pen-raised rams were fed a WGP-containing diet (0, 5% and 10% of dry matter basis) for 74 days. An increase in the concentrations of reactive oxygen species (ROS, P < 0.05) and malondialdehyde (MDA, P < 0.05) were observed in the testes of rams subjected to restraint stress, and dietary WGP supplementation effectively decreased their contents (P < 0.05). Restraint stress reduced both weight and volume of testes, and impaired sperm quality. Dietary WGP supplementation increased testes weight, sperm concentration, motility and acrosomal integrity, and decreased sperm deformity in pen-raised animals (P < 0.05). The total antioxidative capacity (T-AOC) and catalase activity were decreased in the testes of pen-raised lambs (P < 0.05), and T-AOC, catalase, glutathione peroxidase 4 (GPx4) and superoxide dismutase (SOD) activity were increased when rams were fed the WGP-containing diet (P < 0.05). With the exception of SOD and GPx4, the mRNA contents of catalase and nuclear factor-like-2 factor (Nrf2) did not vary among the groups, and greater protein levels of SOD, catalase and GPx4 were observed in WGP-treated lambs (P < 0.05). Taken together, these results suggest that WGP can be used as a feed ingredient in rams to alleviate restraint induced oxidative stress and improve epididymal sperm quality.