Use of Yeast-Fermented Canola Meal to Replace Fishmeal in the Diet of Asian Sea Bass Lates Calcarifer (Bloch, 1790)

Abstract

Fishmeal is a significant protein source for aquatic feed, especially for carnivorous fish. Currently, the price of fishmeal is increasing, also it is mentioned as a competition of human food fish. Replacing fishmeal by other protein sources is therefore an important target. This study tested yeast-fermented canola meal in the diet of Asian sea bass, Lates calcarifer to determine its effects on growth, feed acceptance, feed utilization, nutrient digestibility, body proximate, minerals and their utilization. Diets consisted of a 35% fishmeal base (control) and four diets in which fishmeal protein was replaced by yeast-fermented canola meal at levels of 25, 50, 75 and 100%. For each diet, three groups of fish with an initial weight of 5 g were fed to satiation twice a day for 60 days. Feed intakes and survival rates of test fish fed the diets with up to 50% replacement were not significantly different (P > 0.05). Fish fed the diet with 100% replacement rejected the feed and all died within two weeks. Fish fed the diet in which 75% of fishmeal protein replacement had lower final mean weight, daily weight gain, protein efficiency ratio, nutrient digestibility and higher feed conversion ratio (P < 0.01) than fish fed the control, 25% and 50% replacement diets. Increasing the protein replacement level lowered body crude protein, ash, Ca, Mg, P and their utilization of Asian sea bass (P < 0.05). This seemed to relate to increasing dietary phytic acid as the inclusion level of yeast-fermented canola meal increased. It was concluded that 50% of fishmeal in the diet of Asian sea bass could be replaced by yeast-fermented canola meal without overall impact on growth. This study also showed the possibility of < 10% dietary fishmeal for this species since fish accepted a diet containing only 8.75% fishmeal.