Silydianin Improves the Preservation of Cooled Boar Semen

Cooled boar sperm is susceptible to oxidative stress, therefore, the addition of antioxidants to the extender has been a recurring alternative. The objective of this research was to evaluate the effect of silydianin (SILYD) on the preservation of cooled boar semen. Fifteen ejaculates from five boar were extended and supplemented with SILYD at 10, 20, 40 and 60 μM. Then, the samples were cooled for five days at 16°C. Every 24 h, sperm motility and kinematic were assessed with a computer-assisted sperm analysis (CASA) system. At 0 and 96 h, reactive oxygen species (ROS) and total antioxidant capacity (TAC) were evaluated by fluorescence microplate reader, and functionality membrane integrity (FMI) was assessed by hypoosmotic swelling test (HOST). Sperm viability (SV), lipid peroxidation (LPO), and mitochondrial membrane potential (ΔΨM) were evaluated by flow cytometry. Linear models were adjusted and the comparison of the means was carried out by the Duncan test. A sperm motility index (SMI) was calculated and regression analyses were performed. SILYD20 increased total motility (TM) at 72 h of cooling, and SILYD10, SILYD20 and SILYD40 improved progressive motility (PM) at 72 h of cooling, compared to the control (p < 0.05). Likewise, all treatments with SILYD increased the beat cross frequency (BCF) after 24 h (p < 0.05); and SILYD10 and SILYD40 increased rapid spermatozoa (RS) after 72 h of cooling (p < 0.05). SILYD10 reached the maximum SMI. In addition, the regression analysis showed that SILYD20 had the lowest rate of decline of SMI during the cooling period (p < 0.05). At 96 h of cooling, all SILYD treatments reduced ROS production. Likewise, SILYD10 and SILYD60 increased the TAC assessed by the 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) assay at 0 h, and by the ferric reducing antioxidant power (FRAP) assay at 96 h of cooling, respectively (p < 0.05). At 0 h of cooling SILYD10 produced an increase in FMI (p < 0.05), and a decrease in sperm with non-intact membrane and non-peroxidized lipids (p < 0.05). It is concluded that silydianin improves the quality of cooled porcine semen, and reduces oxidative stress by lowering ROS production and enhancing antioxidant capacity.