Antioxidant effects of zinc-oxide nanoparticles on post-thaw quality and in vivo fertility of Beetal buck spermatozoa

Abstract

Metallic nanoparticles are generally considered potential cryoprotectants during semen cryopreservation owing to their ability to improve the spermatozoa quality following cryopreservation when added in cryo-diluents. The present study aimed at investigating the effects of incorporating zinc oxide nanoparticles (ZnO-NPs) in the cryo-diluent on in vitro post-thaw sperm quality attributes, oxidant-antioxidant profile, and in vivo fertility rate in Beetal buck. After characterization, ZnO-NPs were added to the Tris-citric acid-fructose yolk extender. Semen samples, collected from five breeding bucks (5 ejaculates per buck) using an artificial vagina, were pooled. The pooled semen samples, distributed into five equal aliquots, were diluted in the Tris-citric acid cryo-diluent containing five different concentrations of ZnO-NPs (0.5 mg/ml, 1.0 mg/ml, 1.5 mg/ml, 2.0 mg/ml, and 0.0 mg/ml called control group), and were cryopreserved for 24 h. At post-thaw, various in vitro sperm quality parameters, and antioxidant enzyme profiles like superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), and reduced glutathione (GSH) levels were determined. For the in vivo fertility experiment, breeding does (n = 152), aging from 1.5 to 4 years, were artificially inseminated with spermatozoa with intact acrosome containing the same five concentrations of ZnO-NPs. Results demonstrated that the 1.0 mg/ml ZnO-NPs (crystallite size of 19.73 nm) improved (p < 0.01) the activities of antioxidant enzymes (SOD, CAT, and POD) with concomitantly decreased levels (p < 0.001) of lipid peroxidation (LPO) and reactive oxygen species (ROS) when compared with the other groups. Total spermatozoa motility, rapid velocity, and average path velocity were higher (p < 0.05) with the 1.0 mg/ml ZnO-NPs when compared with the control group. Progressive motility and straight-line velocity were higher (p < 0.05) with the 0.5, 1.0, and 1.5 mg/ml of ZnO-NPs addition compared with the 2.0 mg/ml and control groups. The sperm kinematics parameters; the amplitude of the lateral head displacement, the beat cross frequency, the straightness, and the linearity were not influenced by the ZnO-NPs inclusion. Supra-vital plasma membrane integrity was higher (p < 0.001) with the 0.5 mg/ml and 1.0 mg/ml of ZnO-NPs added groups when compared with either 2.0 mg/ml ZnO-NPs or the control group. The viable sperm with intact acrosome was higher (p < 0.05) in the 1.0 mg/ml ZnO-NPs group compared with the other groups. Low supplementation rates improved (p < 0.05) the DNA integrity when compared with the higher dose (2.0 mg/ml ZnO-NPs). The pregnancy per AI was higher (59.3 %; P < 0.05) in the does inseminated with semen added with the 0.5 mg/ml ZnO-NPs followed by 1.0 mg/ml (58.8 %), 1.5 mg/ml (58.6 %), and 2.0 mg/ml (46.6 %) when compared with the control group (33.3 %). We concluded that the 1.0 mg/ml ZnO-NPs added in the citric acid-fructose yolk extender improved the post-thaw quality of Beetal buck spermatozoa in terms of elevated activities of endogenous antioxidant enzymes, improved structural and functional integrity along with higher fertility.