A bioenergetic model to estimate feed requirement of gibel carp, Carassius auratus gibelio

Abstract

The feeding chart for gibel carp Carassius auratus gibelio was established by energetic modeling. Several sub-models were used as follows: Body energy content: E ( kJ/fish ) = exp ⁡ ( 1.476 + 1.128 × ln ⁡ W ( g ) ) ; Fish growth: SGR e ( % / d ) = exp ⁡ ( − 6.320 + 0.667 × T − 0.011 × T 2 − 0.025 × T × ln ⁡ W ) − 0.25 ; Feces lost: FE ( kJ/d ) = 0.077 × C ( kJ/d ) ; Non-feces excretion (nitrogenous excretion): UE + ZE ( kJ/d ) = 0.052 × C ( kJ/d ) ; Maintenance energy: HE m ( kJ/d ) = exp ⁡ ( − 0.830 + 0.021 × T ⁡ ( ° C ) + 0.670 × ln ⁡ W ⁡ ( g ) ) × 24 × 13.54 / 1000 ; Heat increment: H i ⁢ E ( kJ/d ) = exp ⁡ ( − 6.243 + 0.698 × ln ⁡ W ( g ) + 1.941 * ln ⁡ T ( ° C ) ) . Where the E, SGR e, FE, (UE + ZE), HE m, H i E, W, and T were energy content in fish body, specific growth rate in energy, feces excretion in energy, energy loss in nitrogenous excretion, energy used in maintenance metabolism, energy lost for heat increment, body weight, and water temperature, respectively. The feeding chart was calculated according to the energy budget equation IE = FE + GE + (UE + ZE) + (HE m + H i E) (IE: energy intake (kJ/d); GE: energy in growth (kJ/d); FE: energy in feces excretion (kJ/d); (UE + ZE): energy in nitrogenous excretion (kJ/d); HE m: energy in maintenance metabolism (kJ/d); H i E: energy in heat increment (kJ/d)) based on the above sub-models with the computer program. Sensitivity analysis showed that the sub-model of fish growth was most sensitive in all the models used to calculate the feeding chart at 20 and 35 °C, and that of feeding metabolism was the second most sensitive. Validation experiment was conducted at 27.5 °C with juvenile gibel carp of 6-g initial body weight. The results showed that feed allocation and waste production was reduced while the food conversion efficiency was increased in the fish fed according to the feeding chart compared to the fish fed at maximum rate ( P < 0.05). However, the observed final fish body weight in the validation was significantly less than the predicted value by the model of fish growth ( P < 0.05). Therefore, the feeding chart by energetic modeling of gibel carp could be proposed to aquaculture in practice with the prerequisite in accurate prediction of growth rate.