Selenium, an essential trace element, has functions in reducing oxidative stress and improving reproduction and immune status. A factor that contributes to oxidative stress in pigs is the high growth rate in modern pig production. In addition, during gestation and lactation, sows are confronted with increased levels of oxidative stress, which can harm the development and health of the embryos.
Therefore, high-performing sows require good antioxidant levels. An optimal level of selenium in the diet of pigs is known to protect against the harmful effects of oxidative stress in finishing pigs, sows and their offspring.
Different sources of selenium are available that can be used to enrich the diet, including inorganic forms such as sodium selenite, but also organic forms such as selenised yeasts or L-selenomethionine. Organic selenium (in the form of L-selenomethionine) is preferred as it can be stored in animal proteins – like muscles, colostrum and milk – and can be efficiently transferred to the offspring.
It is therefore hypothesised that organic selenium will have better and longlasting effects in supporting finishing pigs, sows and their offspring during times of oxidative stress. The effects of different selenium sources – including L-selenomethionine in finishing pigs, sows and piglets – were studied in several trials by the Norwegian University of Life Sciences (NMBU) in 2018, 2019 and 2020.
Selenium deposition in finishing pigs
A study with 24 finishing pigs investigated the effects of three selenium-supplemented diets and a non-supple-mented control diet on selenium deposition and immune responses. The selenium-supplemented diets differed in the selenium source: sodium selenite, selenised yeast or L-selenomethionine (Excential Selenium 4000, Orffa).
L-selenomethionine allowed for the highest increase in selenium deposition in muscle tissue (see Figure 1). Other tissue samples also showed higher selenium levels for the group receiving L-selenomethionine in their diet than receiving the other selenium sources. That indicates that L-selenomethio-nine allows for higher selenium storage in body tissue, which animals can use under stress when selenium uptake is limited. Pigs that were supplemented with selenium under normal conditions without a disease challenge showed a better im-mune status and lower levels of inflammatory markers. This is shown by the fact that selenoprotein W (SelenoW) and sele-noprotein H (SelenoH), both selenogenes, were higher expressed in pigs that received additional selenium. Interferon gamma (IFN-γ) and cyclo-oxygenase 2 (cox2) expression, both inflammatory markers, were lower in selenium-supplemented pigs. Organic selenium also allows for a better balanced immune system, which is shown by the reduction in caspase 3 (casp3) expression, involved in apoptosis. When the pigs were challenged with the endotoxin LPS, the important anti-inflammatory cytokine IL-10 was upregulated in the pigs that received L-selenomethionine.