A 2 × 4 factorial experiment was conducted to determine the bioavailability of zinc (Zn) from amino acids chelated (Zn–Am) and glass embedded Zn (Zn–Gl) as sources for rainbow trout, Oncorhynchus mykiss, fed practical type diets. Two levels of Zn (20 and 40 mg kg−1) were supplemented to the diets using either zinc sulphate (Zn–Sf), zinc methionine (Zn–Mt), Zn–Am or Zn–Gl. Rainbow trout with an average weight of 2 g were fed the experimental diets for 15 weeks. Growth and feed gain ratio (FGR) were not significantly influenced by the dietary Zn content and forms. Alkaline phosphatase (ALP) activity for both levels of Zn–Am was significantly higher than that of Zn–Sf and Zn–Gl at 20 mg supplementation. In another experiment, fish of about 95 g were fed the same experimental diets to determine the absorption of Zn and it was found to be significantly higher from Zn–Am compared with the rest. Retention from Zn–Am at 20 mg was significantly higher than the rest, excluding Zn–Sf. The results suggest that the availability of Zn from Zn–Am might be superior among the sources compared.

No 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.