ニジマスに対する各種微量元素無添加魚粉飼料の影響

概要

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Rainbow trout were fed on fish meal diets without a supplement of one trace element (Zn, Mn, Cu, Co) or magnesium (Mg) for 93 weeks in order to investigate the availability to the fish of these minerals contained in white fish meal. Feeding a diet without a supplement of Zn caused cataracts (100%) together with short body dwarfism (80%) and depressed growth. These results were found to be very similar to those obtained in the fish receiving the diet without a supplement of any trace elements. The deletion of Mn or Mg from the mineral mixture in fish meal diets resulted in cataracts; the abnormality was 80% and 29% respectively at the end of the feeding experiment. On the other hand, the growth was not much affected by the deletion of Mn or Co from the diet. The deletion of Zn also resulted in reduced levels of Mn and Cu, and that of Mn, Cu or Co resulted in a low level of Zn in vertebrae. suggesting an interaction between Zn and Mn, or Cu or Co in the fish. Thus, each supplement of dietary Zn, Mn, Cu or Mg is found to be essential for rainbow trout, even though white fish meals contain various kinds of minerals.