Bioavailability and tissue distribution of amino acid-chelated trace elements in rainbow trout Oncorhynchus mykiss

Abstract

: Feeding trials were conducted to determine the availability of amino acid-chelated trace elements to rainbow trout. Three practical diets were supplemented with trace element mix either all from sulfates (Tr-Sf), Zn and Mn from sulfates added with Cu from amino acid chelates (Cu-Am) or a mixture of trace elements from amino acid chelates (Tr-Am). Rainbow trout weighing 1.11 g were fed the experimental diets for 15 weeks. Growth, feed gain ratio (FGR), tissue distribution, retention of the elements and plasma alkaline phosphatase (ALP) activity were compared between the treatments. Absorption of the elements was determined using larger fish of approximately 95 g fed the same experimental diets. Growth and FGR were not significantly influenced by the chemical form of the elements. The highest concentration of Cu was measured in the liver, whereas highest concentrations of Zn and Mn were in bone. Plasma ALP activity was significantly higher in the Tr-Am group. The absorption of elements from the Tr-Am diet was higher but not significantly different from the other two diets. These results suggest that trace elements from Tr-Am seem to be more available than from inorganic sources tested.