Mineral nutrition in fish. XXII. Availability to rainbow trout of zinc contained in various types of fish meals.

Abstract

A feeding experiment was conducted to examine availability to rainbow trout of zinc (Zn) contained in various types of fish meals (white fish meal, brown fish meal, and sardine meal wlth or without solution). Fingerlings weighing 0.7g in average were fed diets containing four kinds of fish meals as protein source with or without supplement of Zn for 27 weeks at water temperature of 10-20°C. The effect of deletion of Zn from the mineral mixture in fish meal diets on growth, appearance of dwarfism and cataract and Zn content in vertebrae was highest in fish fed with white fish meal diet containing a high amount of tricalcium phosphate. While the effect was not so severe in fish fed other fish meal diets containing a lower amount of tricalcium phosphate. These results have clearly demonstrated that availability to rainbow trout of Zn in fish meal was greatly affected by the tricalcium phosphate content. Thus the availability to rainbow trout of Zn contained in white fish meal was lowest among four types of fish meals used due to a highest level of tricalcium phosphate, judging from the growth of the fish, rate of appearance of short body dwarfism and eye lens cataract and Zn content in vertebrae.