Influence de l'agglomération et du stockage des aliments composés sur leur teneur en Canthaxanthine : conséquences sur la digestibilité et la fixation de ce pigment chez la Truite Arc-en-ciel

Abstract

To determine one of the reasons for pigmentation variability in hatchery trout, canthaxanthin losses in 13 samples of carophyll red and 5 samples of 10% hydrosoluble canthaxanthin were examined during the preservation of the feed concentrates (in beadlets) and during the pelleting and storage processes of the feeds. The effects of this degradation on digestibility and on pigmentation of rainbow trout were studied. The protection of canthaxanthin in beadlets is efficient and the various batches were homogeneous; the contents of pure product were steady and corresponded to the theoretical values (10.5 .+-. 0.5 ppm). Though the temperature of the pellets coming out of the press was moderate (43.degree. C), the pelleting process led to a large loss of pigments. This decrease was significant: 20 and 15%, respectively, in carophyll red and 10% hydrosoluble canthaxanthin. During storage of the pellets for 2 mo. under ambient winter temperature before use, a further significant loss of .apprxeq. 17% was recorded regardless of beadlet type. An in vivo test showed a low apparent digestibility of canthaxanthin (20%). These low values may be partially explained by the method used for feces collecting. Though the fixed canthaxanthin/ingested canthaxanthin ratio was near 1%, the trout was strongly colored irrespective of the canthaxanthin preparation used.