Diet digestibility and growth performance of African catfish fed diets with blends of poultry PAP

With the general aim of increasing the efficiency and profitability of market-ready diets tailored for recirculating aquaculture system (RAS), this study evaluated diet digestibility and growth performance of African catfish (Clarias gariepinus) fed four practical diets (CP: 44% DM; EE: 12% DM; GE: 19 MJ kg−1) containing different rates of fishmeal (FM) and blends of poultry processed animal proteins (PAP) meals, i.e. poultry by-product meal, hydrolysed feather meal and poultry dry-blood meal. A total of 600 fish (116 ± 16 g) were randomly distributed into 12 RAS units (3 tanks × treatment) and fed during 84 days with diets based on different levels of FM (from 9 to 1%) and increasing levels of PAP (from 23 to 39%), that is 9FM-23PAP, 5FM-28PAP, 9FM-31PAP, 1FM-39PAP. Fish fed diet 1FM-39PAP showed the lowest protein (–3%) and lipid (–2%) digestibility coefficients and the worst growth performance in terms of final body weight (–18%), total length (–7%), condition factor (–4%), feed intake (–18%), specific growth rate (–14%) and feed conversion ratio (+21%) compared to the other diets (P<0.05). Fish fed intermediate diet 5FM-28PAP reported the highest survival rate (97%) compared to other diets (P<0.001). Overall, also from an economic perspective, high PAP inclusion (39%) associated to very low FM (1%) worsened diet utilization and fish performance, whereas a viable dietary formulation for RAS farming of African catfish should include a more balanced and intermediate levels of the two protein sources.