The effects of Spirulina platensis meal as a feed supplement on growth performance and pigmentation of rainbow trout (Oncorhynchus mykiss)

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 (p < 0.05). However, carotenoid concentrations of skin and fillet significantly increased with increasing the levels of the alga (p < 0.05). 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.

► Effects of Spirulina platensis on the pigmentation and growth of rainbow trout. ► Spirulina can improve fillet pigmentation effectively. ► Growth performance was not influenced by Spirulina inclusion. ► Coloration and carotenoid concentration in rainbow trout were linearly related.