Abstract:
The present study investigated the digestibility of nutrients in cassava leaf protein concentrate for Nile tilapia (Oreochromis niloticus) and African catfish (Clarias gariepinus). Fifty apparently healthy juveniles of the experimental fishes were stocked at 10 fishes per experimental glass tanks, allocated to five dietary treatments. Five dry practical diets (CLPC0, CLPC10, CLPC20, CLPC30and CLPC40) of 0 (control), 10, 20, 30 and 40% replacement value of fishmeal with cassava leaf protein concentrate respectively (formulated and prepared at Nigerian Institute of Oceanography and Marine Research, Lagos), were fed to the fishes twice daily at 5% body weight for 14 days. Faecal samples were collected eight hours after feeding with excess feeds siphoned out 30 minutes after feeding. At the end of each 14-day digestibility trial, faecal samples of O. niloticus and C. gariepinus were analyzed for proximate composition. Apparent digestibility coefficients of nutrients in the diets (protein, energy, lipid, dry matter, organic matter and fibre) were calculated from the proximate compositions of diets and faeces.Apparent digestibility of nutrients in diets fed to O. niloticus varied significantly across the treatments from CLPC0 - CLPC40. Apparent energy digestibility (AED) ranged between 70.33% and 86.25% with the highest (86.25%) recorded in CLPC0 followed by CLPC40 (82.20%). Similar (P>0.05) apparent protein digestibility (APD) (88.93% and 89.83%) were recorded for CLPC0 and CLPC40, while APD of CLPC10 and CLPC20 were similar. Apparent lipid digestibility (ALD) recorded for all the dietary treatments were significantly different (P<0.05) and the values decreased with increasing levels of CLPC in the diets from diets 1 to 5. Apparent dry matter digestibility (ADMD) was between 71.01% and 89.32 % with the highest recorded in the control diet which was similar (P>0.05) with fish fed 40% CLPC.Apparent digestibility coefficients of nutrients in diets fed to C. gariepinus were also sensitive (P<0.05) to inclusion levels of CLPC in the diets. Highest AED (86.44%) was recorded
for C. gariepinus fed CLPC40 which was significantly better than the control treatment (82.75%) and other inclusion levels of CLPC. C. gariepinus fed CLPC0 (control diet) had the highest APD (92.15%) which also compares well with the APD of CLPC40 (89.94%) and CLPC10 (88.01%). Apparent lipid digestibility values ranged between (80.60 and 90.08%) with the highest (90.08%) recorded in CLPC40 which was similar with C. gariepinus fed the control diet. C. gariepinus fed CLPC0 had the highest apparent ash and dry matter digestibility (87.60% and 85.81%) respectively which were similar (P>0.05) with the AAD and ADMD (86.49% and 85.10%) of CLPC40. This study has shown that O. niloticus and C. gariepinus can effectively digest and utilize nutrients in diets containing cassava leaf protein concentrate included up to 40%.
