This study evaluated the effects of diets containing 0, 2.5, 5, 7.5 and 10% Spirulina platensis, and 50 mg of
synthetic astaxanthin kg−1 on skin and fillet pigmentation, and growth performance of rainbow trout
(Oncorhynchus mykiss). A completely randomized experimental design was developed with six treatments
and three replicates. Two hundred and sixteen rainbow trout with average initial weight of 101±8 g were
assigned to eighteen experimental tanks. The experiment lasted for ten weeks. Rainbow trout fed 5% S.
platensis showed a significant lower growth performance than those fed 7.5 and 10% S. platensis (pb0.05).
However, carotenoid concentrations of skin and fillet significantly increased with increasing the levels of
the alga (pb0.05). Inclusion of 10% S. platensis as a natural pigment source resulted in the highest carotenoid
deposition in both tissues. The highest values of a* (redness) and b* (yellowness) were observed in fish fillet
fed 10% S. platensis. In the skin, however, the highest value was found for fish fed synthetic astaxanthin. In
addition, feeding on control diet significantly increased L* (luminosity), C* (chroma), and H° (hue) in both
skin and fillet compared to feeding with other diets. The present results demonstrate that S. platensis can
be introduced as an alternative natural carotenoid source instead of synthetic astaxanthin in rainbow trout
diets. Inclusion of 7.5% S. platensis was found to be a suitable dietary level to ensure pigmentation as well
as no negative effects on fish growth.
This study evaluated the effects of diets containing 0, 2.5, 5, 7.5 and 10% Spirulina platensis, and 50 mg of
synthetic astaxanthin kg−1 on skin and fillet pigmentation, and growth performance of rainbow trout
(Oncorhynchus mykiss). A completely randomized experimental design was developed with six treatments
and three replicates. Two hundred and sixteen rainbow trout with average initial weight of 101±8 g were
assigned to eighteen experimental tanks. The experiment lasted for ten weeks. Rainbow trout fed 5% S.
platensis showed a significant lower growth performance than those fed 7.5 and 10% S. platensis (pb0.05).
However, carotenoid concentrations of skin and fillet significantly increased with increasing the levels of
the alga (pb0.05). Inclusion of 10% S. platensis as a natural pigment source resulted in the highest carotenoid
deposition in both tissues. The highest values of a* (redness) and b* (yellowness) were observed in fish fillet
fed 10% S. platensis. In the skin, however, the highest value was found for fish fed synthetic astaxanthin. In
addition, feeding on control diet significantly increased L* (luminosity), C* (chroma), and H° (hue) in both
skin and fillet compared to feeding with other diets. The present results demonstrate that S. platensis can
be introduced as an alternative natural carotenoid source instead of synthetic astaxanthin in rainbow trout
diets. Inclusion of 7.5% S. platensis was found to be a suitable dietary level to ensure pigmentation as well
as no negative effects on fish growth.
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