Development of pelleted feed for humpback grouper, cromileptes altivelis

Four growth trials were conducted in the effort to develop cost-effective diets for the humpback grouper, Cromileptes altivelis, a notoriously slow growing carnivorous marine fish species. The first three trials were related to the most important macronutrients in fish diets, namely protein, lipid, and carbohydrate, respectively. The findings from these trials were used as the basis for formulation of cost-effectives diets for humpback grouper in the final trial. In the first trial, six experimental diets were formulated to replace fish meal protein with a local poultry by-product meal (PBM) at 50, 75 or 100 % level, or an imported PBM at 75 or 100 % replacement level, respectively. The results from this study indicated that good quality terrestrial PBM can successfully replace more than half the protein from marine fish meal in the diets for humpback grouper. However, total replacement of fish meal with PBM might be constrained by lowered nutrient digestibility and limiting essential amino acids. In the second trial, five fish meal-based practical diets were formulated to contain iso-ingredients but with different sources of lipids [crude palm oil (CPO), refined, bleached, deodorized, palm olein (RBDPO), soybean oil (SBO), or canola oil (CNO)] and their performance compared with the control diet that contained cod liver oil (CLO) as the added lipid source. There were no significant differences (P>0.05) in terms of growth, feed utilization, body indices, and whole-body proximate composition among dietary treatments. Replacement of dietary CLO with the tested vegetable Oils produced fish with lower n-3 highly unsaturated fatty acids and increased levels of 18:2n-6 in the muscle and liver. The present study demonstrated that various vegetable oils can be used in fish meal-based dietary formulation for humpback grouper without compromising growth or feed utilization efficiency. In the third trial, the effect of dietary carbohydrate sources and levels on growth and feed utilization of humpback grouper was examined. Six experimental diets were formulated to contain corn starch, tapioca starch or dextrin at 10% and 20% inclusion levels. The growth, feed utilization efficiency, and body indices of humpback grouper were independent of carbohydrate levels and sources. In view of the lower price of tapioca starch than the price of corn starch and dextrin, inclusion of tapioca starch in the practical diets for humpback grouper will be able to reduce feed cost. In the final trial, two diets (U-MS/SM1 and U-MS/SM2) were formulated with a blend of ingredients based on the result of the previous three trials. The performance of the experimental diets was compared with a locally sourced marine fish feed, an imported marine fish feed, and trash fish. Growth and FCR of humpback grouper fed experimental diet U-M/SM2 were superior to other fish groups. FCRs of the pelleted feed ranged from 1.3 to 2.4 and Significantly better (P<0.05) than the trash fish (5.0). The survival rate of fish fed trash fish was also significantly lower (P