Effects of a Partial Replacement of Fish Meal by Cheddar Cheese By-products on Growth Performance,Body Composition and Plasma Biochemical Indices of Juvenile Rainbow Trout(Oncorhynchus mykiss)

An 8-week growth trial was conducted to evaluate the effects of a partial replacement of fish meal by cheddar cheese by-products(CCB) on growth performance,body composition and plasma biochemical indices of juvenile rainbow trout(Oncorhynchus mykiss).Four isonitrogenous and isoenergetic diets were prepared with CCB to replace 0,15%,30% and 45% of protein supplied by fish meal and meanwhile the soybean oil was gradually decreased,and were named as C0,C15,C30 and C45,respectively.Forty juvenile rainbow trout with initial average body weight of(5.73±0.00) g were randomly assigned to each tank with 4 replicates for each treatment in recirculation system.The results showed as follows: compared with control group(C0 group),all growth indices of juvenile rainbow trout in C15 and C30 groups were not significantly different(P0.05),while dairy feed intake(AFI),weight gain rate(WGR) and specific growth rate(SGR) of juvenile rainbow trout in C45 group were significantly decreased(P0.05).Condition factor(CF),viscerasomatic index(VSI),hepaticsomatic index(HSI) and body composition of juvenile rainbow trout in C15 and C30 groups were not significantly different compared with control group(P0.05),however,the body ash content of juvenile rainbow trout was significantly higher than that in control group(P0.05).No significant differences were observed in plasma biochemical indices between control group and C30 group(P0.05).In conclusion,CCB can replace 30% fish meal protein(9.6% of fish meal,and the soybean oil supplementation from 5% to 3%,concurrently) in juvenile rainbow trout diets with no significant effects on growth performance,body composition and plasma biochemical indices.