Effects of organic selenium on thrombocytes and parasite infestation in nile tilapia juveniles

The knowledge of fish mineral requirements, such as selenium, is important to promote the growth and health status for fish in captivity, but excess or deficiency must be avoided. Therefore, this study evaluated the growth performance, hematology and the parasite load of Nile tilapia (Oreochromis niloticus) supplemented with organic selenium (0.0; 0.25; 0.5; 1.0 and 1.5 mg/Kg). The increased levels of selenium did not affect significantly (p<0.05) the growth performance of tilapia. However, the increases of thrombocytes and parasite load are proportional to the increases of selenium levels. Unlike expected, supplemented diets with selenium did not benefit growth performance and supplementation of 1.5 mg/kg caused deleterious effects on the health of tilapia.