Alternative Protein Sources As Substitutes For Fishmeal In The Diet Of Young Tilapia Oreochromis Niloticus (LINN.)

Abstract

Fifteen test diets were theoretically formulated to contain 33.32% dietary protein, dry matter, using a mixture of alternative protein sources and fishmeal in various proportions. Test diets were fed to fingerlings (initial weight 3.2±0.2 g) in triplicate tanks for eight weeks at 5% body weight per day in three portions. At the end of each experimental phase, fish carcass from the feeding groups was homogenized. Freeze-dried samples of fish at the beginning and end of the experiments as well as samples of the test diets were analyzed for proximate composition. Fish fed diet 1 containing 43% fishmeal recorded the highest weight gain, highest specific growth rate (SGR, 3.46%/d) and lowest food conversion ratio (FCR, 1.11). When part of the fishmeal was substituted with 18% soy- bean meal and 5% blood meal (diet 8), SGR and FCR were 3.02%/d and 1.34, respectively, not significantly different from diet 1 at 0.05 probability. Results showed that proper combination of alternative protein sources can provide 42-45% of the protein required by Oreochromis niloticus (33.32% dietary protein, dry matter). In such a combination, soybean meal can replace up to 25% of the fishmeal as a protein source. Blood meal exceeding 6%, groundnut cake beyond 10%, soy- bean meal above 20%, and wheat bran beyond 10% retarded fish growth. High mortality was gen- erally observed when these levels were exceeded, even in only one of the protein sources.