Digestibility of astaxanthin and canthaxanthin in rainbow trout as affected by dietary concentration, feeding rate and water salinity

Abstract

The digestibility of astaxanthin and canthaxanthin in rainbow trout was studied in two different experiments. In the first experiment, the trout were fed, at a rate of 1.0% body weight/day (BW/d), diets containing various concentrations (12.5, 25, 50, 100 and 200 mg carotenoid/kg feed) of astaxanthin or canthaxanthin in fresh water. The overall apparent digestibility of astaxanthin was higher than that of canthaxanthin whatever the dietary concentration of the carotenoid. Apparent digestibility coefficients were maximum for astaxanthin (79.1 ± 1.3%) at 25 mg/kg feed and for canthaxanthin (68.6 ± 2.8%) at 50 mg/kg feed, and then decreased at higher dietary levels of carotenoids. In the second experiment, only diets containing 25 or 50 mg carotenoid/kg feed of either of the two carotenoids were fed to trout in fresh water at feeding rates of 0.5,1.0 and 1.5% BW/d, and in sea water (30-32 ppt) at a rate of 1.0% BW/d. Neither the feeding rate nor the salinity affected the digestibility of the two carotenoids.