In livestock production, selenium additives mainly includeInorganic selenium (sodium selenite, sodium selenate), organic selenium (yeast selenium, selenomethionine), nano selenium.
Inorganic selenium has high toxicity and low utilization rate. Compared with inorganic selenium, organic selenium has higher absorption and utilization value and less acute toxicity, and is considered to be a better selenium product. At present, organic selenium has gradually replaced inorganic selenium to be popularized.
With the further study of selenium additives,Nano-selenium due to itsHigh bioavailability and low toxicitycaused widespread concern in the livestock industry. Compared with sodium selenite, selenomethionine and other selenium supplement products, nano-selenium not only has better absorption efficiency but also has a strong advantage of low toxicity and high efficiency.(Xu et al., 2003;Zhang et al., 2005, 2008 ;Wang et al., 2007).
Inacute toxicityOn the other hand, the poisoning doses of inorganic selenium and organic selenium were 15 mg/kg and 49 mg/kg, respectively, while the nano selenium was 113 mg/kg.
Nano-selenium is the least acute toxic selenium supplement found so far..
Absorption of inorganic selenium and organic selenium
Inorganic selenium in the body is achieved throughpassive absorptionThe way is absorbed by the intestine, such as sodium selenite is absorbed in a simple diffusion form, and sodium selenate is absorbed in a co-transport manner. Inorganic selenium into the animal after the intestinal tract, onlySmall amounts of selenium involved in binding to form selenoproteinsBy the body to use, most of the selenium into the kidney by metabolism, low utilization rate.
While selenomethionine is similar to the amino acid transport mechanism, it isactive absorptionof(Combs et al.). Therefore, selenomethionine has a higher absorption availability than sodium selenite.
Characteristics and Absorption of Nano-Selenium
Nanoselenium is a zero-valent organic selenium with protein as the core, red elemental selenium as the membrane, and protein as the dispersant.
High-quality nano-selenium hasthermal stability, It is not easy to convert into gray or black element selenium, it is easily soluble in water, and its absorption rate and activity are high.Studies by Zhang et al. have shown that the size of nanoparticles has an important influence on the biological function of nano-selenium, and nano-selenium with smaller particle size has higher biological activity.
There are two main ways for animals to absorb nano-selenium, one isActive Transshipmentmechanism way through the intestinal wall into the body, the other ispassive diffusionways to be absorbed.The number of surface atoms and the number of dangling bonds and unsaturated bonds of nanoparticles are more, so that they haveHigher surface activity, its physical adsorption and chemical adsorption capacity is much greater than the bulk material, which is easy to be directly absorbed by the animal gastrointestinal tract.(Chen Hui et al., 2005).
The results show that the effect of adding nano selenium on the selenium content in the tissue is more obvious than that of adding sodium selenite, and it also has an increasing trend compared with organic selenium (Shi Liguang et al., 2009).
