Replacement of fish meal by rendered animal protein ingredients with lysine and methionine supplementation to practical diets for gibel carp, Carassius auratus gibelio

The effect of partial replacement of fish meal (FM) by rendered animal protein ingredients: poultry by-product meal (PBM) and meat and bone meal (MBM), alone or in combination, with lysine and methionine supplementation in the practical diets for gibel carp was studied. Eight isonitrogenous (crude protein 37.5%) and isolipidic (crude lipid 7%) diets were formulated to feed juvenile gibel carp (initial body weight 13.45 ±0.04 g fish− 1) for 12 weeks. Diet 1 (control) was a high quality commercial gibel carp diet, containing 18% FM as the sole animal protein source without amino acids (AAs) supplementation. In the other seven diets (Diets 2–8), 33.3–100% of FM protein was replaced by PBM, or a blend of PBM and MBM. Lysine (Lys) and methionine (Met) were supplemented to Diets 2–8 in order to match the AAs profile of the control diet. The results showed a significant difference in final individual body weight (FBW) and specific growth rates (SGR) among fish groups (P < 0.05). Fish fed the test groups showed no significant difference compared with the control group except for fish fed Diet 8. The highest FBM and SGR were recorded in fish fed Diet 5, which contained the combination of 9% PBM and 4.5% MBM to replace 67% FM protein with Lys and Met supplementation. Carcass composition, CF, HSI and VSI among all groups at the end of the experiment were not significantly affected by the dietary treatments. The optimal replacement level of FM by the combination of PBM and MBM, with Lys and Met supplementation, was shown by third-order polynomial regression analysis to be 66.7% in protein.