Selenium (Se) is important in this respect as it is a vital component of selenoenzymes (e.g. glutathione peroxidase), which play a role in reducing ROS and therefore maintain antioxidant status.
A continuous, optimal selenium supply is difficult to maintain as uptake from the diet will be impaired when high stress (e.g. sickness) is present. At that moment selenium is in high demand, for the production of selenoenzymes, and a storage inside the animal would be beneficial.
Maintaining an optimal selenium status - A nutritional solution
Selenium can be added to the diet in either inorganic or organic forms. The advantage of using organic selenium (L-Selenomethionine) over inorganic sources (e.g. sodium selenite or selenate) is its ability to be incorporated directly into animal proteins. This incorporated selenium acts as a storage depot of selenium inside the animal.
L-Selenomethionine is the only selenium compound that can be directly, without conversion, built into animal structural proteins (e.g. muscle and liver). This ensures optimal selenium supply, even during stressful periods when it is in high demand by the animal.
L-Selenomethionine has traditionally been supplied to the diet via addition of selenised yeast. However, the yeast approach is limited. Normally, around 63% of the total selenium in a selenised yeast is present as L-Selenomethionine but there is a huge variation between products and batches. The percentage of selenium present as L-Selenomethionine can be as low as 18%! The remaining selenium in yeast cells is present in forms that are no more active than much cheaper inorganic selenium. The introduction of Excential Selenium 4000 (Orffa, The Netherlands) into the market now provides a superior option to optimally supply animals with L-Selenomethionine.
The success of L-Selenomethionine in swine
Literature shows that L-Selenomethionine supplementation during pregnancy is an excellent way of increasing the selenium and antioxidant status of sows and their piglets.
This supplementation helps to lower oxidative stress-related effects (e.g. smaller litter size and birth of weak lethargie piglets) .. Falk et al. (2019) evaluated the effect of L-Selenomethionine in sows on feed intake, haematological and biochemica[ parameters as well as total selenium in plasma, colostrum and milk. Supplementation was initiated 30 days prepartum and continued throughout the lactation period.
Results showed significantly increased total selenium levels in colostrum (x2) and in milk (x3) compared to the control diet (sodium selenite supplement).
Total plasma selenium was not significant different between groups. Feeding of diets supplemented with L-Selenomethionine led to higher concentrations of SelP and SeAlb, selenoproteins active in selenium transport from extramammary tissue to colostrum and milk, at farrowing.
A higher amount of selenium in colostrum and milk is beneficial as it strengthens the piglets' antioxidative system, passive immunity and improves their weight gain. In this trial, interestingly, higher average daily feed intake (ADFI) was observed during the lactation period.
From day 13 post-partum until the end of the study, the ADFI was significantly higher in the SeMet supplemented group.