Mixtures of oilseed meals as dietary protein sources in diets of juvenile Nile tilapia (Oreochromis niloticus l.)

Abstract

The suitability of different mixtures of soybean meal (SBM), cottonseed meal (CSM) and groundnut cake (GNC) as ingredients to replace fish meal in the diets of Nile tilapia (Oreochromis niloticus L.), was evaluated over a 56-day growth period. Nine isonitrogenous (320g.kg^-1), isolipidic (100 g.kg^-1) and isoenergetic (18 KJ.g^-1) test diets were formulated in which different mixture combinations of SBM, CSM and GNC proteins replaced fish meal (FM) protein at levels of 50% and 75%. The control diet had FM as the sole protein source. Fish were fed at 6 - 4% body weight per day. The growth experiment was conducted in plastic tanks in a recirculation system. Each dietary treatment was in triplicate. Growth performance and feed utilization of fish fed with the oilseed meal mixtures indicated that up to 50% replacement could be more effective than a single source for the substitution of fish meal in tilapia diets. This was particularly evident with the diet containing equal proportions of all oilseed meals (EQ50). Combination of oilseed meals in different proportions was more effective than the single individual sources. This could be due to a compensatory effect which led to some reduction of antinutritional factors coupled with improved essential amino acid profile in the diet as a result of mixing.

Keywords: Oilseed meals, Nile tilapia, protein sources, mixtures, growth performance