Effects of Arthrospira platensis on growth, skin color and digestive enzymes of Koi, Cyprinus carpio

Abstract

This study evaluated the effects of diets containing 0, 2.5, 5, 7.5 and 10% Arthrospira platensis on skin pigmentation, growth performance, and digestive enzymes of (Koi, Cyprinus carpio). A completely randomized experimental design was developed with five treatments and three replicates. One hundred and fifty koi fish with average initial weight of 30±1g were assigned to fifteen experimental tanks. The experiment lasted for eight weeks. Koi fish fed with 5% A. platensis showed a significant lower growth performance than those fed with 7.5 and 10% A. platensis (p<0.05). However, carotenoid (astaxanthin) concentrations of skin significantly increased with increased levels alga (p<0.05). Inclusion of 10% A. platensis as a natural pigment source resulted in the highest astaxanthin deposition in skin. The highest values of a* (redness) and b* (yellowness) were observed in fish skin fed with 10%A. platensis. The results demonstrate that A. platensis can be introduced as a natural carotenoid source in koi fish diets. The activities of protease, amylase and lipase in dietary supplementation of A. platensis were significantly higher than those of the control group. Liver enzymeze also decreased significantly by dietary supplementation (p<0.05). However, inclusion of 5-10% A. platensis in diets did appear to have a significant positive effect on growth rates, pigmentation, and improvement of digestive and liver enzymes activities.