What is sodium selenite?
Sodium selenite is the sodium salt of selenous acid, a white crystalline, water-soluble compound in which selenium is in the +4 oxidation state. The pure substance contains about 45% selenium.
Because the pure compound is highly toxic and only milligrams of selenium are needed per kilogram of feed, it is rarely handled as such in feed mills. It is supplied as standardised pre-dilutions on a carrier (commonly 1% Se or less), which are then incorporated into the mineral premix under controlled conditions.
What does selenium do in animal feed?
- Antioxidant defence: selenium is part of glutathione peroxidases, enzymes that break down peroxides and protect cell membranes, working together with vitamin E.
- Thyroid function: selenium-dependent deiodinases convert thyroxine (T4) to the active hormone T3.
- Muscle health: selenium and vitamin E deficiency is associated with nutritional muscular dystrophy (white muscle disease) in calves and lambs and related disorders in other species.
- Reproduction: adequate selenium supports fertility and is associated with fewer retained placentas in dairy cows.
- Immunity: selenium supports normal immune cell function.
Sodium selenite compared with organic selenium
Selenium from sodium selenite is well absorbed and is used efficiently for the synthesis of selenium-dependent enzymes. However, it is not stored in body proteins, so it builds up smaller reserves and transfers less selenium to eggs, milk and the foetus than organic selenium sources such as selenium yeast or hydroxy-selenomethionine.
Sodium selenite is economical and well established, and it is often combined with an organic source in the same premix. It is a reactive oxidising compound, so it should not be mixed directly with reducing agents or some vitamins in concentrated form.
How is the selenium level assessed?
Soil selenium varies widely between regions, so forages and grains grown in low-selenium areas contribute little selenium. Nutritionists set the supplemental level according to species, production stage, the selenium status of local raw materials and the vitamin E level of the diet.
Selenium is strictly regulated because of its narrow safety margin. In the EU, total selenium in complete feed is limited to 0.5 mg/kg (at 12% moisture), with a separate cap on the amount added as organic selenium. Local regulations and the product label always prevail.
Quality and safety criteria
- Guaranteed selenium content of the pre-dilution, verified by analysis.
- Homogeneity of the pre-dilution: an even distribution on the carrier is essential for accurate dosing.
- Carrier quality and compatibility with the rest of the premix.
- Safe handling: dust control, personal protective equipment and clear labelling, because concentrated selenite is toxic.
- Certificate of analysis (CoA) and lot traceability.
CTF Premix and sodium selenite
Sodium selenite can be included in CTF Premix's mineral and vitamin-mineral premixes according to the customer's formulation, alone or together with organic selenium. It is incorporated in pre-diluted form, with mixing procedures designed for micro-ingredients, at our Ankara facility under ISO 9001:2015 and GMP, and every lot has a certificate of analysis and lot traceability.
This page is for general information. Inclusion rates and product choice should be decided with a nutritionist, taking into account the species, the feed formulation and the applicable regulations.