In swine, most artificial inseminations (AI) are routinely conducted with cooled spermatozoa (Waberski et al., 2019), since AI with frozen spermatozoa yields inferior performance (Yeste, 2016).That may result from injuries in spermatozoa attributed to cold shock during freezing and thawing. Also, boar spermatozoa have high content of unsaturated fatty acids in their plasma membrane and limited intracellular antioxidant mechanisms, being prone to oxidative stress due to lipoperoxidation and to the production of reactive oxygen species (ROS) (Cerolini et al., 2000). Thus, inclusion of antioxidants in extenders for sperm freezing can mitigate oxidative stress.One of such antioxidants would be vitamin E, which is a natural component of spermatozoa's antioxidant system (Lenzi et al., 1996).Positive effects of vitamin E on post-thawing quality have been reported for spermatozoa of men (Taylor et al., 2009), bulls (Nasiri et al., 2012) and boars (Peña et al., 2003;Satorre et al. 2007). Other potentially efficient antioxidant is resveratrol, a molecule found in grapes which has anti-inflammatory properties, but low stability and solubility (Vitaglione et al., 2005). Positive effects of resveratrol were described for human (Branco et al., 2010), bull (Bucak et al., 2015 and buffalo spermatozoa (Longobardi et al., 2017), but negative effects were reported for ram spermatozoa (Silva et al., 2012). Data for boar spermatozoa revealed no effect on post-thawing quality, but positive effects on in vitro oocyte penetration (Gadani et al., 2017).
