adequate body development and reproductive
performance, and aiding the immune system to neutralize
free radicals and protect the body against infections
(Surai, 2000; Rayman, 2000; Surai, 2002).
Despite being essential for animal metabolism, selenium
levels in almost all feedstuffs are not sufficient to supply
animal requirements.
Selenium is usually supplemented in broiler diets in its
inorganic form (sodium selenite). However, this salt is very
toxic, and needs to be solubilized in its ionic form in order
to be absorbed in gastrointestinal tract.
In addition, the electric charges of this ionic form may interact
with other diet components (minerals, proteins and
carbohydrates), rendering them partially unavailable to
animals (Rutz et al. 2004).
This has stimulated research on the use of organic selenium
in animal diets to improve its bioavailability. This
study aimed at evaluating the effect of organic selenium
dietary supplementation on the immune response of broilers
vaccinated against viral diseases and coccidiosis.