Evaluation of Schizochytrium sp. as a source of DHA and Haematococcus pluvialis as a source of astaxanthin pigment in diets for farmed salmonids

Abstract

Two studies were conducted to evaluate the digestibility of docosahexaenoic acid (DHA)-rich Schizochytrium sp. (Sc) in diets for Atlantic salmon (Salmo salar) and to assess the fillet pigmenting efficacy of a weakened whole cell Haematococcus pluvialis (Hp) in diets for rainbow trout (Oncorhynchus mykiss). Apparent digestibility coefficients (ADCs) for Sc by Atlantic salmon for DHA, lipid, protein, and energy, lipid, and DHA were 96.3%, 67.1%, 93.9%, and 70%, respectively. Pigmentation of rainbow trout by Hp biomass (0.31% Ax by dry weight) showed no significant (p>0.05) differences in growth, Ax digestibility (76.7%), fillet Ax content (8.86 mg/kg), retention (15.4%), L*a*b*, or SalmoFan™ readings between diets containing Hp and synthetic Ax. Sc is a highly digestible source of polyunsaturated fatty acids and DHA, and the weakened-cell Hp ingredient is a bioavailable source of Ax that can achieve flesh coloration levels comparable to that of synthetic Ax in diets for farmed salmonids.