Carotenoids in diets for salmonids: V. Pigmentation of rainbow trout and sea trout with astaxanthin and astaxanthin dipalmitate in comparison with canthaxanthin

Abstract

Rainbow trout ( Salmo gairdneri Richardson) and sea trout ( Salmo trutta L.), kept in fresh water, were fed diets containing either 30 mg synthetic astaxanthin (a 1:1:2 mixture of the three optical isomers 3 S, 3′ S, 3 R, 3′ S) plus 30 mg cantaxanthin/kg (diet i) or 30 mg synthetic astaxanthin dipalmitate (as astaxanthin equivalents) plus 30 mg canthaxanthin/kg (diet ii). The flesh was more efficiently pigmented in rainbow trout than in sea trout. Astaxanthin and canthaxanthin were deposited to the same extent when fed in a mixture. Astaxanthin dipalmitate was deposited in the flesh as free astaxanthin and more slowly than canthaxanthin, resulting in enhanced canthaxanthin deposition with diet ii. High values for apparent digestibility of the carotenoids were found but this was partly ascribed to breakdown of the carotenoids in the intestine or faeces. Analysis of the optical isomers of astaxanthin in the flesh demonstrated an increased level of (3 R,3′ R)-astaxanthin and a reduced level of (3 S,3′ S)-astaxanthin in both rainbow trout and sea trout fed the diet containing astaxanthin dipalmitate.