Utilization of carotenoids from various sources by rainbow trout: muscle colour, carotenoid digestibility and retention

Rainbow trout (Oncorhynchus mykiss) with a mean (SD) weight of 120 (2)g were fed diets supplemented with astaxanthin extracted from the yeast Phaffia rhodozyma (OY1 = 50 mg carotenoids kg super(-1) feed, OY2 = 100 mg carotenoids kg super(-1) feed), astaxanthin (AX = 100 mg astaxanthin kg super(-1) feed) and canthaxanthin (CX = 100 mg canthaxanthin kg super(-1) feed) for 4 weeks. Muscle analyses at the end of the experiment indicated a significantly higher carotenoid concentration in the AX group, while CX and OY1 groups were similar in spite of the differences in dietary concentration. The measure of total muscle colour difference ( Delta E* sub(ab)) between initial samples and 4 week ones was higher for the AX fish group but showed no significant difference between OY1, OY2, and CX. The hue and the reflectance ratio (R sub(650):R sub(R510)) of fish muscle increased in proportion to carotenoid intake. Digestibility (ADC) of yeast astaxanthin in OY1 and OY2 groups was significantly higher than that in the AX group. Canthaxanthin ADC was about one sixth of that of astaxanthin (AX group). Carotenoid retention in the muscle, expressed as a percentage of carotenoid intake, was higher for the AX group than that recorded for OY1 and OY2. According to ADC, carotenoid retention showed a marked lower value for the CX group. Muscle retentions were similar for astaxanthins from both sources.