Abstract Cryopreservation reduces ram sperm viability and fertilizing ability by inducing oxidative stress, membrane damage, and DNA fragmentation. This study evaluated whether adding chitosan-stabilized nano green tea extract (Nano-GTE) to a Tris-soybean lecithin extender improves post-thaw semen quality and fertility of Ossimi rams. Ejaculates (pooled from five mature rams) were extended with Tris-soybean lecithin containing 0 (control), 50, 100, 150, or 200 µg/mL Nano-GTE, equilibrated at 5 °C for 4 h, frozen in 0.25 mL straws, stored in liquid nitrogen and thawed at 37 °C for 30 s. Post-thaw progressive motility, viability and membrane integrity were significantly higher in the 100 µg/mL group (PrM: 46.3 ± 0.21% vs. control 41.5 ± 0.22%; Viability: 47.1 ± 0.27% vs. control 42.8 ± 0.24%; Membrane integrity: 47.6 ± 0.26% vs. control 43.9 ± 0.27%; P < 0.001). DNA fragmentation (Comet assay) was lowest in the 100–150 µg/mL groups (DNA damage: 5.0 ± 0.21% at 100 µg/mL vs. control 8.3 ± 0.21%; P < 0.001). Antioxidant capacity (TAC) in the post-thaw medium increased at 100 µg/mL, while markers of membrane damage (MDA, AST, ALT, LDH) were reduced compared with control ( P < 0.05). Fertility (pregnancy rate after cervical AI) was higher with semen from the 100 and 150 µg/mL groups, whereas the 200 µg/mL dose impaired some parameters. Together, these results indicate that supplementing a Tris–soybean lecithin extender with Nano-GTE at 100 µg/mL markedly improves the post-thaw quality and fertility of ram sperm; higher doses (≥ 200 µg/mL) may be detrimental.
Gabr et al. (Wed,) studied this question.