Effects of Deletion of Several Trace Elements from Fish Meal Diets on Growth and Mineral Composition of Rainbow Trout Fingerlings

Abstract

This study was conducted to determine the effect of deletion of Zn concurrently with Mn or Cu from fish meal diets on growth of rainbow trout and the concentration of these trace metals in the fish. Rainbow trout fingerlings were fed on fish meal diets without supplement of total or each trace element for 40 weeks.
The deletion of both Zn and Mn at the same time from the diets resulted in the most reduced growth. The effect of deletion of Zn alone or simultaneously with Cu or Mn affected the growth of fish more seerely than of the total deleetion of trace elements But the highest percentage of cataracts and short body dwarfism resulted from the deletion of the single trace element Zn.
The Zn level of eyeballs was affected most severely by the deletion of Zn from the diet. The content of Zn, Mn and Cu in stomach was found to be proportional to that of these metals in the fish meal diets.
The growth and feed effciency were not improved by elevating the concentration of trace metals derived from white fish meal, indicating a low availability of minerals in the white fish meal for this fish.