Given the same dietary carotenoid inclusion, Atlantic salmon, Salmo salar (L.) display higher blood levels of canthaxanthin than astaxanthin

Atlantic salmon, Salmo salar , fitted with permanent dorsal aorta cannulae were fed diets containing either 0, 30, 60 mg kg(-1) or combinations of astaxanthin and canthaxanthin, with the aim of comparing the uptake efficiencies to blood of the two pigments and evaluating possible interactions during absorption when formulated in the same diet. Given either astaxanthin or canthaxanthin in separate diets, at dietary levels of <30 mg kg(-1), an identical linear relationship (R-2=0.97) between dietary levels and blood concentrations was observed for both carotenoids. At dietary astaxanthin inclusions above 30 mg kg(-1) , blood astaxanthin concentration approached saturation at an average level of 1.2+/-0.04 mug mL(-1) (arithmetic mean+/-SD), whereas blood levels of canthaxanthin continued to increase linearly throughout the inclusion range tested (0-60 mg kg(-1)). When both carotenoids were presented in the same diet, a reduction in the absorption efficiency of both pigments was observed (P<0.05). This manifested itself as a lower level in blood than the level observed when each carotenoid was administered separately. The negative interaction was most prominent for astaxanthin, the maximum average blood saturation level of which fell (P<0.05) to 0.73+/-0.03 mug mL(-1) (arithmetic mean+/-SD). Our data support the conclusion that at higher dietary inclusions, canthaxanthin is more efficiently absorbed from the digestive tract into the blood of S. salar than astaxanthin.