Effect of different levels of nanoliposome-coated astasxanthin on growth performance, body proximate composition, liver enzyme activity and pigmentation of rainbow trout (Oncorhynchus mykiss)

The purpose of this study was to investigate the effect of different levels of nanoliposome-coated astaxanthin (NA) on growth performance, body proximate composition, liver enzyme activities and pigmentation in rainbow trout (Oncorhynchus mykiss). Groups of fish weighing 31 ± 2 g each in three replicates (30 fish per replicate) were fed with 0, 25, 50, 75 and 100 mg/kg nanoliposome-coated astaxanthin for 60 days. At the end of the experiment, growth performance including final weight, weight gain (WG), feed conversion ratio (FCR), specific growth rate (SGR), survival rate (SR), daily growth rate and condition factor (CF), body crude protein, fat, ash and moisture, liver enzymes (ALT and ALP) and pigmentation (skin and muscle carotenoids and muscle astaxanthin) were measured. The results showed that the addition of NA had a significant effect on growth indices (p < 0.05). The highest final body weight (FBW) (101.46 ± 4.46 g) was related 75 mg/kg NA, and the lowest FBW (93.10 ± 0.96 and 91.98 ± 4.08 g) was seen in control and 100 mg/kg NA respectively (p < 0.05). Also, the highest amounts of protein and ash were measured in 50 and 75 mg/kg NA treatments, while the lowest levels of these occurred in control and 100 mg/kg NA. The highest amount of serum ALT and ALP enzymes was in 100 mg/kg nanoliposome-coated astaxanthin treatment, and the lowest amount of ALT enzyme was in 50 mg/kg treatment. Also, the lowest amount of ALP enzyme was obtained in control treatment. The concentration of carotenoids in skin and fillet and fillet astaxanthin increased significantly by adding nanoliposome-coated astaxanthin to the diet (p < 0.05). The highest carotenoid quantity of skin and fillet and astaxanthin fillet was observed in fish fed 75 mg/kg nanoliposome-coated astaxanthin and the lowest amount in the control group. These results suggest that the incorporation of nanoliposome-coated astaxanthin into rainbow trout diet at the level of 75 mg/kg can have a positive effect on growth indices, reduced liver enzyme activity and improved skin and fillet pigmentation.