Effect of green tea extracts and green tea grounds as dietary supplements on cultured yellowtail and Ayu

Yellowtail (Seriola quinqueradiata) and "Ayu" (sweet fish, Plecoglossus alt ivelis) are most commonly cultured fishes in Japan. Body lipid contents of these cultured fishes are much higher than those of natural fishes because of over supplements of lipids in diets to promote growth. On the other hand , production of canned tea drinks has been increasing for the last few year s. Greater parts of tea grounds which is byproducts of tea drinks are disca rded. In the present study, the effects of green tea extracts and grounds o n growth and lipid content in two types of cultured fishes were examined. I n yellowtail, the accumulation of body lipids was suppressed by the supplem entation of 3.6% green tea grounds and 0.7% green tea extracts in the diets . In Ayu, it was suppressed by the supplementation of 1% green tea extracts in the diets, while the effect of tea grounds were not significant. The fi shes cultured by the green tea extracts or tea grounds-supplemented diets w ere commonly decreased in average body weights. but their condition factors were kept at the same levels as the control.