Could addition of resveratrol improve fertility rate of boar insemination doses

The exposure of spermatozoa to reactive oxygen species (ROS), produced mostly by cellular metabolism, induces a loss of motility, which is directly correlated with the level of oxidative stress endured by the spermatozoa. Oxidative stress affects several sperm function, resulting, amongst others, in impaired motility and sperm-oocyte binding, which could lead to lower fertility rate (Aitken e Baker, 2006. Mol Cell Endocrinol. 250:66-69). In this regard, resveratrol (RVT), a polyphenol compost, which plays an important role as antioxidant, due to its capacity to inhibit ROS formation (Stojanovic et al., 2001. Archives of Biochemistry and Biophysics, 391:79-89), has been used to improve sperm quality of different species with promising results (Bucak et al., 2015. Andrologia, 47: 545-552). Thus, the current study was carried out to evaluate whether the addition of RVT would exert a positive effect in fertility rate of boar sperm cooled at 17˚C for 72 h. For this purpose, females (n = 30) were fixed-timed inseminated after hormonal protocol with altrenogest (20 mg/day during 18 days), eCG (600 UI, IM) after 72 hours of altrenogest withdraw porcine LH (2.5 mg, IM) was administered then, 36 hours later, intra-uterine insemination was performed with pooled semen from two boars. After initial semen analysis, raw semen was extended in BTS medium (50 x 106 spermatozoa/mL in 50 mL) and RVT was added to form the following treatments: T0 (BTS + RVT 0 mM) without RVT, T1 (BTS + RVT 0.01 mM. Samples were cooled for 72 h before inseminations. Females were slaughtered for embryo collection five days after insemination in order to evaluate fertility rate of viable embryos (number of viable embryos/sum of oocytes and total embryos). Females inseminated with seminal doses containing RVT exhibited lower rates of viable embryos than those inseminated with seminal doses in the absence of RVT (59.96 ± 46.35a ; 12.15 ± 23.91b , to T0 and T1 respectively). Thus, the presence of 0.01 mM of RVT in insemination doses has impaired fertility rate represented by viable embryos. Successful in sperm fertilization needs a capacitation step, which includes some necessary oxidative events. In this study, we possibly caused an imbalance in oxidant-antioxidant factors in favor to antioxidant, inhibiting the physiological oxidative events, and consequently impairing fertility rate. In conclusion, our results showed that the addition of RVT is not recommended, in concentration higher than 0.01 mM. However, additional studies of concentrations lower than 0.01 mM of RVT in boar insemination doses are needed to clarify these effects.