Effects of dietary supplementation with krill meal on pigmentation and quality of flesh of rainbow trout (Oncorhynchus mykiss)

Effects of administration of krill meal (KR) and synthetic astaxanthin (AS) during the finisher phase of the fattening cycle of rainbow trout were studied on flesh pigmentation and quality traits. The inclusion of krill meal increased the body weight and size and decreased the perivisceral fat and visceral weight indexes. AS diet produced the highest accumulation of total carotenoids in the fillet compared to KR diet: difference was significant after 15 days of feeding (2.55 vs 2.14 mg/kg) to the end of trial (5.76 vs 4.82 mg/kg). The same pattern was observed for astaxanthin concentration with the highest values in the fillet of fish fed AS diet. Fillet lightness (L*) was not affected by trout diets whereas redness (a*) and yellowness (b*) were significantly higher in fish fed the AS diet till 30 day of the trial. Hue was not affected by feeding, whereas Chroma was significantly higher in AS fish throughout the trial excepted on 45 d sampling. Using SalmoFan scale, trout fed KR diet had paler pink-red colour than those receiving AS diet. No significant differences emerged in proximate composition and cholesterol content of trout in the two groups. The fatty acid profile of the fillets reflected fatty acids of the diets administered to trout. EPA, DPA, DHA and total n-3 were significantly higher in KR fish.