Bioavailability of amino acids chelated and glass embedded zinc to rainbow trout, Oncorhynchus mykiss, fingerlings

A 2 x 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-G1 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-Arn 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.