Replacement of fish meal in diets for Australian silver perch, Bidyanus bidyanus -: V.: Least-cost formulation of practical diets

Silver perch fingerlings (80.7 +/- 1.2 g) were stocked at a density of 15,000 fish ha(-1) in earthen ponds (0.1 ha) and cultured for six months to a market size of > 350 g fish(-1). Fish were fed a reference diet (SP35; 27% fish meal) or one of two test diets formulated using a least-cost linear feed formulation program and digestibility coefficients for a range of Australian agricultural products (meat meal and plant proteins). In the test diets, all but 5% (95LC2) or 10% (95LC1) of the fish meal was replaced. Survival was high (> 95%) in all ponds. There was no significant difference between the performance of silver perch fed the two test diets. The mean weights (431.9 g and 439.8 g), daily growth rates (2.5 g fish(-1)) and FCRs (2.0 and 1.9) of fish fed 95LC1 and 95LC2, respectively, were significantly different (P < 0.05) from the weight (395.4 g), daily growth (2.2 fish(-1) day(-1)) and FCR (2.2) of fish fed SP35. The diet ingredient cost to produce 1 kg fish was significantly lower for 95LC2 than the costs of the other diets AUD$:1.06 vs. 1.52; P < 0.05. Diet did not significantly affect body composition (nitrogen, fat, ash or energy) or sensory quality of the fish. These results show that least-cost diets containing meat meal and plant proteins (as replacements for all but 5% fish meal) are suitable for silver perch grown to market size in earthen ponds. (C) 2000 Elsevier Science B.V. All rights reserved.