Effects of tribasic copper chloride on growth, copper status, antioxidant activities, immune responses and intestinal microflora of blunt snout bream (Megalobrama amblycephala) fed practical diets.

摘要

A study was conducted to investigate the effects of dietary tribasic copper chloride on growth, copper status, antioxidant activities, immune responses and intestinal microflora in blunt snout bream, Megalobrama amblycephala. Eight practical diets containing different levels of copper (0, 3, 6, 9, 25, 50, 100 and 150 mg Cu kg-1) from tribasic copper chloride were fed to blunt snout bream (31 g of initial average body weight) in quadruplicate groups in outdoor cages. Growth, copper status, antioxidant activities, immune responses and intestinal microflora were analyzed after a 56-day feeding period. Weight gain and specific growth rates in fish fed diets supplemented with 3-6 mg Cu kg-1 were significantly higher than those in fish fed the control diet (which supplemented with 0 mg Cu kg-1) (p<0.05). Fish fed diets supplemented with 9 mg Cu kg-1 had significantly lower feed conversion ratio than fish fed the control diets (p<0.05). Copper concentrations in liver, kidney and intestine were significantly higher in fish fed diets with 50-150 mg Cu kg-1 than those in fish fed the control diet (p<0.05). Dietary copper at levels ranging from 9 mg kg-1 to 100 mg kg-1 significantly enhanced T-AOC activities (p<0.05). In addition, diets supplemented with 100-150 mg Cu kg-1 significantly increased activities of AKP and ACP (p<0.05). Intestinal bacterial community structures in fish fed diets supplemented with 6-150 mg Cu kg-1 were different from those in fish fed diets supplemented with 0-3 mg Cu kg-1. The study showed that diets supplemented with 3-6 mg Cu kg-1 could meet the copper requirements for blunt snout bream fed practical diets; diets supplemented with 9 mg Cu kg-1 could increase feed efficiency; diets supplemented with 100 mg Cu kg-1 could increase activities of AKP and ACP and affect intestinal microflora structure, though leading to a status of increasing copper accumulation in tissues.