Investigation of the effects of copper source, copper and zinc levels, and dietary protein source on CU bioavialability in rainbow trout

Abstract

Limited research has examined the effects that plant-based diets have on copper (Cu) and Zinc (Zn) absorption and utilization in rainbow trout. Few studies have been conducted to determine if interactions exist in the utilization of Cu when increasing levels of supplementary Zn were offered. The objectives of this research were to: first determine what effect protein source (plant vs. animal based), Cu source (complex vs. inorganic) and concentrations of Cu (0, 5, 10, 15, 20 ppm) in the diet had on rate and efficiency of gain and Cu tissue levels in rainbow trout. The second experiment was to determine if interactions occur due to increasing diet content of Zn (0, 30, 300, 1500 ppm) and Cu provided at two levels (0 or 10 ppm) on tissue levels of Cu in rainbow trout. From experiment one, trout fed plant-based diet had higher (P < 0.05) ADG and improved (P < 0.05) FCR in comparison to fishmeal fed trout. Highest (P < 0.05) hepatic Cu concentrations were also observed in trout fed plant-based diets. No differences (P >0.05) were observed in growth or hepatic concentrations due to Cu source. From experiment two, no antagonistic interactions were observed between increasing levels of dietary Zn and Cu. Trout fed the two highest levels of dietary Zn (300 and 1500 ppm) had the greatest (P < 0.05) weight gains. Dietary Zn supplementation increased (P < 0.05) whole body Cu at 12 wks. With increasing dietary Zn supplementation, resulted in increased (P < 0.05) whole body Zn. Cataracts and tail rot were observed at 12 wks in trout fed the Cu and Zn deficient diet. In conclusion, plant-based diets enhanced Cu bioavailability indicated by higher weight gains and hepatic Cu concentrations in experiment one, compared to trout fed fishmeal-based diets. Cu supplementation is required in a plant-based in order to achieve optimal growth in trout. Results of the second study indicate rainbow trout fed plant-based diets require Zn supplementation to obtain sufficient growth. The highest levels of Zn supplementation did not impair Cu uptake in rainbow trout.