Effect of dietary protein levels on growth performance, hematological profile and biochemical composition of fingerlings rainbow trout, Oncorhynchus mykiss reared in Indian himalayan region
Imtiaz Ahmed, Ishtiyaq Ahmad
Abstract
A 10-week feeding trial was undertaken to determine the optimum dietary protein requirement of fingerling rainbow trout, Oncorhynchus mykiss. Six casein-gelatin based isocaloric (20.90 kJ 100 g−1, gross energy) diets containing graded levels of dietary protein (300–550 g kg−1 crude protein) were formulated. Twenty fingerlings (1.56 ± 0.22 g; 5.80 ± 0.50 cm) were randomly stocked in triplicate groups in 75 L circular trough fitted with continuous flow-through system (water volume 2–2.5 L−1) and fed experimental diets at 5% BWday−1 at 0800, 1200 and 1700 h. Significant (P < 0.05) differences in live weight gain, specific growth rate (SGR), feed conversion ratio (FCR), protein efficiency ratio (PER) and body protein deposition (BPD) were noted. Quadratic regression analysis of SGR, FCR, PER and BPD data indicated requirements for dietary protein at 464.5, 471.0, 444.0 and 449.6 g kg−1 of dry diet, respectively. Maximum protein, low moisture and intermediate body fat contents were recorded with fish fed at 450 kg−1 protein diet, while highest HSI value was observed at lowest protein level. Significant differences (P < 0.05) were also observed in Hb, Hct and RBC values of fish fed varying protein diets. Based on the above results, it is recommended that rainbow trout fingerlings require protein in the range of 450–471 g kg−1 for its optimum growth and efficient feed utilization.