Supplemental effect of metallic nanoparticles on cryopreserved semen quality, lipid peroxidation, sperm head ultrastructure and field fertility levels in crossbred (Hampshire x Niang Megha) boars

Reactive oxygen species (ROS) produced by sperm contributes to oxidative stress (OS), leading to a decline in sperm quality. Different antioxidants have shown potential in preventing such damage. The present study explored the effect of metallic nanoparticle (NPs) supplementation on sperm quality in cryopreserved boar spermatozoa. Forty-two (42) ejaculates (7 ejaculates per animal) were collected from six (6) physically and sexually healthy and fertile Lumsniang (Hampshire x Niang Megha) crossbred boars, aged 18-42 months and then diluted in Beltsville thawing solution (BTS) extender containing the different treatments (CON: no NP addition; 10 μM ZnO NPs, 1 μg Se NPs and 0.192 mg Fe₃O₄ NPs per mL of semen). Semen was diluted, packed into 0.5 mL French medium straws, and subsequently frozen in liquid nitrogen (LN₂). Sperm quality, lipid peroxidation (LPO), antioxidant enzyme levels, ultrastructural sperm head morphology and field fertility levels were determined. Significantly (p < 0.05) higher sperm in vitro quality attributes were recorded in the zinc oxide (ZnO) and selenium (Se) NP treatments in comparison to CON whereas iron-oxide (Fe₃O₄) NP treatment significantly (p < 0.05) lowered sperm quality. Post-thaw LPO levels significantly (p < 0.05) decreased in the ZnO and Se NP groups when compared to CON. LPO levels were significantly (p < 0.05) higher in the Fe₃O₄ NP group. The ZnO and Se NP treatments showed significantly (p < 0.05) higher post-thaw antioxidant enzyme levels. Ultrastructurally, Group 1 spermatozoa were significantly (p < 0.05) higher and Group 2 were significantly (p < 0.05) lower in the ZnO and Se NP supplemented group in comparison to CON. No significant (p > 0.05) difference was observed in the in vivo pregnancy rate; however, the ZnO and Se NP treatments significantly (p < 0.05) enhanced the average litter sizes at birth and weaning compared to CON. In conclusion, 10 μM ZnO and 1 μg Se NPs improved post-thaw quality of boar spermatozoa and safeguarded the ultrastructure of their membranes. On the other hand, 0.192 mg Fe₃O₄ NPs had deleterious effects on sperm in vitro quality.