The Israeli Journal of Aquaculture - Bamidgeh 53(1), 2001, 34-43

ALTERNATIVE PROTEIN SOURCES AS SUBSTITUTES
FOR FISHMEAL IN THE DIET OF YOUNG TILAPIA
OREOCHROMIS NILOTICUS (LINN.)

Johnny O. Ogunji and Manfred Wirth

Institute of Freshwater Ecology and Inland Fisheries, Department of Inland Fisheries, Müggelseedamm 310, D-12587 Berlin, Germany

(Received 22.2.01, Accepted 2.5.01)

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% soybean 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%, soybean meal above 20%, and wheat bran beyond 10% retarded fish growth. High mortality was generally observed when these levels were exceeded, even in only one of the protein sources.

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