Earlier studies have shown that Nile tilapia, halibut and gilthead sea bream (Sparus aurata) fed diets without vitamin E supplementation had significantly decreased HSI, likely due to tissue degeneration.
It has also been found that HSI value is correlated with the amount of fat deposition in livers.
Thus, although liver lipid content was not determined in the present study, the non-significant differences among HSI of fish in various treatments may indicate that supplementation of 50 mg vitamin E/kg (112 mg/kg total vitamin E) was sufficient to prevent degeneration and/or fat infiltration of liver tissue in Nile tilapia fed diets containing6 to 14% lipid.
This level of dietary vitamin E was also adequate for normal formation and development of blood cells as none of the hematological parameters evaluated differed among treatments.