SYNERGISTIC REACTIONS BETWEEN VITAMIN EAND SELENIUM IN DIETS OF HYBRID TILAPIA (OREOCHROMIS NILOT1CUS X OREOCHROMIS AUREUS) AND THEIR EFFECT ON THE GROWTH AND LIVER HISTOLOGICAL STRUCTURE

Abstract

Eight experimental diets representing two levels of vitamin E (low 100 IU /kg diet and high 300 IU/kg diet) with four levels of selenium ( 0;2 ; 4 ; 8 mg/kg diet ) were tested on hybrid tilapia (-Qr-niloiieusX JX~mweu8~ ) for a period of 120 days . "The study was performed in outdoor cement ponds, each divided to units by nets with an area of 10m each. Each treatment was performed in duplicates, using 40 experimental fish with an initial weight of 48.83 g on the average . After the adaptation period, the fish were fed on the experimental diets at a rate of 3% of the treatment bibmass dialy, divided into two equal portions at 10. 0 a.m and 2 p.m. Water temperature ranged between 28J to 3L5 °C during the experimental period. Water quality parameters (dissolved oxygen, ammonia oED were within the permissible levels for tilapia. Results obtained^ surhmenzed/in the followingr 1-Hybrid tilapia fea on 2mg Se with 300 IU vitamin E/kg diet had significantly higher (p < 0.05) specific growth rate (SGR), feed conversion efficiency and also improved feed conversion ratio than that fed on the other diets.2-At constant dietary vitamin E level, total serum protein increased with increasing Se level up to 8 mg/ kg diet.3-Fish fed on high level of supplemented vitamin E (300 IU/kg) diet without selenium deprivation, showed increased growth rates and improved feed conversion rate than that fed on the low vitamin E (lOOIU/kg dry diet).4 - The histological investigation showed remerkable effects in the liver tissue of hybrid tilapia fed on dietary Se- supplemented level up to 8mg/kg diet with low vitamin E (lOOIU/kg dry diet) with different degrees of injuries, including blood vessels, hemorrhages and degeneration in hepatic cells, dilatation, odema and hemosidren, hemolysis, necrosis and activation in nuclear division.This study suggests that supplementation of Vit. E 300IU/kg with selenium up to 2 mg / kg dry diet for hybrid tilapia is warranted to increase growth rate and prevent fish from increased concentration of waterborne Se up to toxicity levels.