Effects of natural and synthetic pigments in diets on flesh coloration and growth of rainbow trout (Oncorhynchus mykiss W.)

Abstract

The desired pink to red color of rainbow trout flesh (Oncorhynchus mykiss W.) can be obtained by adding carotenoids to the fish diet. This study was conducted to determine the effects on growth and color retention of natural pigments (30 ppm red pepper meal, 60 ppm red pepper meal, 30 ppm shrimp by-products meal, 60 ppm shrimp by-products meal), synthetic carotenoids (30 ppm astaxanthin, 60 ppm astaxanthin), and a control group (no added pigment). Duplicates of each of the seven treatments were reared for three months. The best specific growth rates were obtained with 30 ppm astaxanthin (0.83%) and 60 ppm red pepper meal (0.84%); the low- est was in the control (0.54%). The lowest food conversion ratio was obtained with 30 ppm astax- anthin (1.38) and highest in the control (2.23; p<0.05). Visual coloration values ranged from 14.46±0.23 in the 30 ppm astaxanthin group to 11.55±0.25 in the control. Retention coefficients ranged from 6.63 in the 30 ppm astaxanthin group to 1.79 in the 60 ppm shrimp by-products meal (p<0.05). Tristimulus chromometer a values ranged from 0.87±0.47 in the control to 6.96±0.47 in the 60 ppm astaxanthin treatment, b values from 10.94±0.27 in the control to 12.90±0.27 in the 60 ppm red pepper meal treatment, and L values from 46.81±0.50 in the 60 ppm astaxanthin group to 54.57±0.26 in the control (p<0.05).