Use of dried layer waste in diets for the hybrid catfish Clarias macrocephalus X C-gariepinus

The feasibility of using dried poultry (layer) waste (DLW) as a substitute for some conventional ingredients in formulated diets was determined for a hybrid catfish Clarias macrocephalus x C. gariepinus. Four isonitrogenous (30% protein) experimental diets were formulated with different amounts of DLW: 0% (diet 1), 12% (diet 2), 24% (diet 3), and 36% (diet 4). Each diet was fed to apparent satiation for 10 weeks to three replicates of 20 fish (2-3 g each) stocked in 200-L fiberglass tanks with flow-through water and air supply. The growth rate of fish decreased at the highest DLW level. No significant differences in weight gain were observed in the fish fed diets containing up to 24% DLW. Feed conversion ratio and protein efficiency ratio were poorest for the fish fed 36% DLW; those ratios did not differ (P > 0.05) for fish fed the other diets. There were no significant differences for apparent net protein retention among treatments; however, apparent net energy retention of fish fed diets with more than 12% DLW was significantly lower (P < 0.05) than that of fish fed the diet with no DLW. Body compositions of fish did not differ significantly among dietary treatments except for body lipid, which tended to decrease with increasing DLW in the diets.