Selenium in sow nutrition

Selenium (Se) is shown to be an essential element for sow nutrition and a great deal of information has been accumulated for the last two decades indicating that dietary form of Se is a major determinant of its efficiency. Indeed, there are two major Se sources for pigs, namely inorganic selenium (mainly selenite or selenate) and organic selenium in the form of selenomethionine (SeMet; mainly as Se-yeast or SeMet preparations). The aim of the review is to update existing information about Se roles in sow nutrition with a specific emphasis to the oxidative stress and possibilities of decreasing negative consequences of the stresses by using dietary Se supplementation in an optimal form. It has been clearly shown that organic selenium has many important advantages in sow nutrition in comparison to traditional sodium selenite. The aforementioned benefits of organic selenium for sow include: better Se status of sows, especially in the case of advanced parities; improved antioxidant defences of sows; increased Se concentration in colostrum and milk and improved antioxidant status of colostrum and milk; improved Se transfer via placenta; improved Se status of foetus and development of pig embryos. It was proven that replacement of sodium selenite by organic Se in the sow's diet improved Se status of newly born piglets characterised by increased Se concentrations in tissues and whole body. In particular, increased Se concentration in piglet muscles could be considered as an important storage form of Se to be used in stress conditions. Furthermore, organic Se in sow's diet (versus sodium selenite) provides better Se status and antioxidant status of weaning piglets, as well as improves thyroid metabolism and increases activities of major digestive enzymes in piglet pancreas at time of weaning. However, most of the commercially relevant parameters (growth rate, mortality, FCR, etc.) were not affected. Only in two most recent publications in which sodium selenite was replaced by pure organic Se source in the sows diet, there were significant improvements in weaning litter weight and average weight of progeny piglets and daily weight gain of piglet from birth to weaning. Indeed, additional well-designed organic Se trials with big numbers of sows in commercial conditions are needed to explore a full potential of organic Se in sow nutrition.