Inclusion of different blends of poultry processed proteins in practical diets for African catfish (Clarias gariepinus) reared in RAS: Effects on nutrient digestibility, growth performance and fillet quality

The present study aimed to test the effects of different dietary inclusion levels of fishmeal (F) and blends of poultry processed protein meals (P), i.e. poultry by-product meal, hydrolysed feather meal, dry-blood meal in African catfish (Clarias gariepinus). Fish were fed during 84 days with four practical diets, i.e. diet HF-LP (F: 90 g kg⁻¹; P: 227 g kg⁻¹), diet MF-MP (F: 45 g kg⁻¹; P: 280 g kg⁻¹), diet HF-HP (F: 90 g kg⁻¹; P: 315 g kg⁻¹), and diet LF-HP (F: 10 g kg⁻¹; P: 392 g kg⁻¹). Fish fed diet LF-HP showed the lowest protein and lipid digestibility coefficients (82 % and 92 % vs. 84 % and 94 %, respectively; p<0.05) compared to fish fed the other diets, and the worst performance in terms of final body weight (551 g vs. 673 g), feed intake (247 g d⁻¹ vs. 301 g d⁻¹), condition factor (0.83 vs. 0.86), specific growth rate (2.69 % d⁻¹ vs. 3.14 % d⁻¹), and feed conversion ratio (1.34 vs. 1.11) (p<0.001). Fish fed diet MF-MP reported the highest survival rate compared to other diets (96.8 % vs. 94.5 %; p<0.001). Fish fed diets with the highest inclusion rates of poultry by-product meal (140 g kg⁻¹ or 165 g kg⁻¹) and hydrolysed feather meal (125 g kg⁻¹ or 135 g kg⁻¹) were associated with the lowest fillet yield (46.2 % vs. 47.1 %) respect to fish fed the other diets (p<0.05). In conclusion, a diet with 10 g kg⁻¹ of fishmeal and 392 g kg⁻¹ of a blend of poultry processed animal proteins is not suitable to sustain the performance of African catfish, whereas a diet with a minimum content of fishmeal at 45 g kg⁻¹ and a blend of poultry processed animal proteins at about 280 g kg⁻¹ could be technically and economically attractive for the RAS farming of this species.