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

This study evaluated the effects of diets containing 0, 2.5, 5, 7.5 and 10% Arthrospir platensis on skin pigmentation, growth performance, and digestive enzymes of koi, Cyprinus carpio. A completely randomized design was performed 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 2.5% A. platensis (1.17±0.02) showed a significant lower growth performance than those fed with 7.5 and 10% A. platensis (1.39±0.02 and 1.46) (p<0.05). However, carotenoid (astaxanthin) concentrations of skin significantly increased with increased levels of dietary algae (p<0.05). The highest values of a* (red zones) and b* (yellow zones) were observed in fish skin fed with 10% A. platensis (4.33±0.15, 5.23±0.15, 5.23±0.15, 5.7±0.36, and 6.33±0.32, respectively). The activities of protease, amylase and lipase in dietary supplementation of 10%A. platensis were significantly higher than those of the control group (protease from 5.17±0.76 to 11 , amylase from 22±1.73 to 32.67±1.53 and lipase from 16.33±2.08 to 74.33±1.53. Liver enzymes also decreased significantly by increased dietary supplementation. (ALT: from 192.33±5.5 to 80.67±1.52, AST: from 1741.7±18.92 to 712.33±10.5, ALP: from 452.33±8.14 to 48±1, LDH: from 7287.3±34.64 to 7119.7±17.89). These results revealed that inclusion of 5-10% A. platensis in diets has a significant positive effect on growth rate, pigmentation, and improvement of digestive and liver enzymes activities in koi fish.