Impact of selenium nano-particles in semen extender on bull sperm quality after cryopreservation.

The aim of this study was to evaluate the effect of adding different concentrations of selenium nano-particles (Se-NPs) in semen extender on bull sperm cryopreservation. Five healthy, fertile Friesian bulls were used, and the ejaculates were obtained using an artificial vagina. Semen of all bulls were pooled and diluted in a tris-yolk fructose (TYF) extender supplemented with Se-NPs at concentrations of 0 (T1, control), 0.5 (T2), 1.0 (T3) and 1.5 (T4) μg/ml for a final sperm concentration of 80 × 106 sperm cells/ml. Diluted semen was packed in straws (0.25 ml) and stored in liquid nitrogen (-196 °C) for one month. After thawing, semen of each treatment was evaluated for sperm quality parameters, including sperm progressive motility, livability, morphological abnormalities, plasma membrane integrity and chromatin integrity. Apoptosis and sperm ultrastructure were also examined. Total antioxidant capacity and lipid peroxidation markers were determined in seminal plasma of semen in each treatment. Finally, the effect of Se-NPs on fertilization capacity was checked in vivo using n = 81cows. Results showed that T2 and T3 had a positive effect (P < 0.05) on post-thawing sperm progressive motility, livability and membrane integrity as compared with the control. Percentage of viable sperm increased (P < 0.05), while percentages of early apoptotic, apoptotic and necrotic sperm cells decreased (P < 0.05) in T3 as compared to T1. Total antioxidants capacity (TAC) in seminal plasma increased (P < 0.05) and malondialdhyde (MDA) concentration decreased (P < 0.01) in T3 as compared to T1, but did not differ in T4 from that in T1. In vivo fertility rate was higher in T3 (90%) than in T1 (59%). In conclusion, enrichment of semen extender with Se-NPs at a concentration of 1.0 μg/ml improved post-thaw sperm quality of Holstein bulls, and consequently in vivo fertility rate by reducing apoptosis, lipid peroxidation and sperm damage occurring by cryopreservation.