Pigmentation of rainbow trouts (Oncorhynchus mykiss) fed two levels of astaxantin in their growing-fattening diets. Pigmentación de trucha arco iris (oncorhynchus mykiss) tipo mar alimentadas con dos niveles de astaxantina en dietas de crecimiento-engorda

Abstract

The color in salmonids is the main condition for an appropriate trading. This color is a result of the retained pigment incorporated to their diets. The present study was conducted to evaluate the pigmentation degree, color, costs of diets and the productive performance of rainbow trouts fed 25 and 80 ppm of astaxantin (AXT), respectively. A total of 200 chilean trouts (Cofradex variety), with an initial weight of 180 g, were used. They were randomly assigned to 2 treatments with 100 fishes each. The group fed 80 ppm of AXT, was considered the control one, because this was the more common level of inclusion when the assay was run. The productive performance was evaluated considering the average weight, feed consumption, feed conversion efficiency, specific growth rate, mortality, factor of condition, growth percentage and pigment retention percentage. The color intensity was evaluated using the "Colour Chart" and "Colour Salmo-Fan by Roche Lab." The pigmentation, the pigment concentration in the flesh, was evaluated by high resolution liquid chromatography (HPLC). The productive performance results were similar between both treatments (p>0,05), but the pigment retention in the flesh throughout the assay was double in the group fed 25 ppm of AXT as compared with controls (p<0,05). At the end of the trial, the pigmentation values obtained were 20 and 15 ppm of AXT for groups fed 80 and 25 ppm, respectively (p<0,05). The color obtained with both levels of pigment in the diets, were within the minimum required levels for normal commercialization of rainbow trouts fillets. The lower incorporation of AXT allowed a reduction of 2,2 times in the cost of pigment incorporation in the diets, this result could be an excellent alternative for the producers to improve their efficiency in the world market of cultivated salmonid