Studies On Replacement Of Fish Meal By Rendered Animal Protein Ingredients In Practical Diets For Gibel Carp, Carassius Auratus Gibelio (Bloch)

The effect of the replacement of fish meal (FM) protein by rendered animal protein ingredients in the practical diets for gibel carp was studied. The test diets matched the essential amino acid (EAA) profile of the control diet by adding a combination of Lysine (Lys) and methionine (Met) or adjusting the proportions of the rendered animal protein ingredients.The replacement of FM protein by poultry by-product meal (PBM) and meat and bone meal (MBM), alone or in combination, with Lys and Met supplementation in the practical diets for gibel carp was studied in Experiment 1. Diet 1 (the control diet) was a high quality commercial gibel carp diet, containing 18% FM as the sole animal protein source without amino acids supplementation. In the other seven diets (Diet 2 - 8), 33.3% - 100% of FM protein was replaced by PBM, or a blend of PBM and MBM, the test diets matched the EAA profile of the control diet with Lys and Met supplementation. Triplicate groups of fish (initial body weight 13.45±0.04 g fish^-1) were fed eight isonitrogenous (crude protein: 37.5%) and isolipidic diets (crude lipid: 7%) for 84 days in the growth experiment. After the growth experiment, a 14 days digestibility experiment was conducted to examine the apparent digestibility coefficient (ADC) of the experimental diets in gibel carp. The highest Final body weight (FBW) and Specific growth rate (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. FBM and SGR of fish fed Diet 4, 7, 8 (without FM) was significantly lower than Diet 5 group, and Diet 8 . group is the lowest, while other groups showed no significant differences. Feeding rate (FR) for Diet 8 group was significantly lower than Diet 5 group, while other groups showed no significant difference with each other. Feed efficiency ratio (FER), Condition factor (CF), Hepatosomatic index (HSI), Viscerasomatic index (VSI), carcass composition (without viscera) of each diet group was not significantly affected by the diet treatments. The EAA profile of the carcass was similar in different diet groups. 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. ADC of dry matter (ADC_D) for Diet 5 and Diet 6 groups showed no significant difference with the control group, but others were significantly lower than the control group. ADC of protein (ADC_P) for Diet 2, 5, 6 groups showed no significant difference with the control group, but others were significantly lower than the control group. ADC of lipid (ADC_L) for Diet 2, 3, 5 groups showed no significant difference with the control group, but others were significantly lower than the control group.The replacement of FM protein by the different proportions of PBM, MBM and blood meal (BM) in the practical diets for gibel carp was studied in Experiment 2. Diet 1 (the control diet) was the same commercial gibel carp diet of the control diet in Experiment 1. In the other seven diets (Diet 2 - 8), 33.3% - 100% of FM protein was replaced by PBM, MBM and BM, and the test diets matched the EAA profile of the control diet. Triplicate groups of fish (initial body weight 15.26±0.04 g fish^-1) were fed eight isonitrogenous (crude protein: 37.5%) and isolipidic diets (crude lipid: 7%) for 84 days in the growth experiment. After the growth experiment, a 14 days digestibility experiment was conducted to examine ADC of the experimental diets in gibel carp. FBW and SGR of fish fed Diet 8 which contained the lowest FM (3% FM dry matter) was significantly lower than the control group, while other groups showed no significant differences. FER of the Diet 8 group was significantly lower than Diet 1, 2, 4, 7 groups. FR, CF, HSI, VSI and carcass composition (without viscera) of each diet group was not significantly affected by the diet treatments. The EAA profile of the carcass was similar in different diet groups. Results indicated that combination of PBM, MBM and BM can replace at least 66.7% FM protein in practical diets for gibel carp. ADCd for Diet 3, 6, 7 groups showed no significant difference between the control group, but others were significant lower than the control group. ADC_P of Diet 2 and Diet 6 groups showed no significant difference between the control group, but others were significantly lower than the control group. ADC_L of different diet groups showed no significant difference except Diet 4 group.Cost analysis showed that ingredient cost, feed price and production cost of the tested diets in both experiments were lower than the control one. It can be conclude from this study that if the EAA profile of the replaced diet is formulated as similar as the practical diet, rendered animal protein ingredients can replace at least 66.7% FM protein of present practical diet for gibel carp without any negative effects on its growth performance, feed utilization and carcass composition. The formulation of Diet 4 and Diet 7 in Experiment 1 and Diet 7 in Experiment 2 can be used to improve the quality of present practical diets of gibel carp.