THE STUDY ON MICROALGAES APPLICATION IN FEEDING OF JUVENILE Koi AND Litopenaeus vannamei LARVAE
A current concern in aquaculture is the application of new source of microalgaes in feeding of aquatic animals. In this study, Scenedesmus and Picochlorum.sp were tested in feeding of juvenile Koi and Litopenaeus vannamei larvae, respectively in two trials. In Trial 1, five isonitrogenous and isolipidic diets with 0% microalgae, 7.5% or 15% Spirulina, 7.5% or 15% Scenedesmus, respectively were fed twice daily to the quadruplicate tanks of juvenile Koi (average initial body weight of 3.60g) in recirculated-water system for 9 weeks. The results showed that fish fed diet with 15% Spirulina powder had significantly higher weight gain (WG), specific growth rate (SGR) and feed efficiency (FE) than other groups (P<0.05). The concentration of malondialdehyde, total antioxidant activity, superoxide dismutase and glutathione transferase activities in serum and liver were not significantly different among all groups (P>0.05). However, total carotenoid continents in scales and fins of juvenile Koi fed dites with either Spirulina or Scenedesmus as well as in frontal head skin of fish fed diet with 15% Scenedesmus increased significantly (P<0.05). The results suggested that Spirulina could improve growth and both Spirulina and Scenedesmus could darken body red color to enhance the ornamental value of Koi. In Trial 2, commercial start feed with spirulina, spirulina and Picochlorum sp. were fed four times daily to the triplicate tanks of Litopenaeus vannamei nauplius (15 thousand in each 300L tank). After 7 days of metamorphosis, the survival rates of larvae fed with commercial spirulina and spirulina were significantly higher than that fed with Picochlorum sp. (P<0.05), which suggested that Spirulina could be a good source of start feed to improve the survival rate of larvae after metamorphosis in Litopenaeus vannamei.