Plasma carotenoid concentration indicates the availability of dietary astaxanthin for Atlantic salmon, Salmo salar

Abstract

Atlantic salmon with an initial weight of 1.1 kg were fed three extruded diets with different amounts of astaxanthin (5, 51 and 61 mg kg −1) in an experiment lasting for 26 weeks. Availability of astaxanthin was assessed after collection of blood plasma from 2 × 10 fish per pen (three pens per diet; two groups of fish per pen, previously unpigmented and pigmented prior to the start of the experiment). The salmon weighed 2–2.5 kg at the time of blood sampling. Correlations were made between mean values for plasma carotenoid concentration and dietary astaxanthin concentration, flesh carotenoid concentration at 24 weeks of feeding, and the amount of carotenoids (mg) retained in flesh per kg body weight increase. There were no differences observed in plasma astaxanthin concentration between salmon which were pigmented or unpigmented prior to the study. The correlation between plasma astaxanthin concentration and dietary astaxanthin concentration was r = 0.90. Plasma astaxanthin concentration and mg astaxanthin retained in flesh per kg body weight increase were also highly correlated ( r = 0.92), as was the correlation between plasma astaxanthin concentration and flesh carotenoid level ( r = 0.95). Plasma astaxanthin concentrations ranged from 0.5 to 5 μg ml −1.