Waste from the biscuit and noodle industries in Nile tilapia diets

The objectives of this work were to determine the apparent digestibility coefficients (ADC) of dry matter (DM), crude protein (CP) and gross energy (GE) of coconut biscuit residues (CBR), sweet biscuits (SBR) and noodles (NR) for Nile tilapia and evaluate the performance of fingerlings fed with diets containing the residues with the highest nutritional value. In the digestibility study, 72 juveniles (with an average weight of 70.5 ± 2.7 g) were organized in a completely randomized design with three treatments and three replications (12 fish per replication). ADC was determined using an indirect method in which 0.10% chromium oxide (Cr2O3) acted as an indicator. To evaluate performance, 225 fingerlings (with an average weight of 3.4 ± 0.5 g) were distributed across 15 tanks (150 L), creating a completely randomized design with five treatments and three replications. The test diets contained 0, 4, 8, 12 or 16% CBR. ADCDM, ADCCP and ADCGE for each of the different residues were, respectively: 85, 88 and 86% for CBR; 32, 51 and 46% for SBR; 24, 31 and 26% for NR. The inclusion of CBR significantly affected final weight of the fish, specific growth rate and protein retention rate, as well as the carcass composition values for dry matter, mineral matter, gross energy and ethereal extract. CBR presents better digestibility than the other tested residues and it can be used as a substitute for maize meal in quantities up to 11.62%, thus improving fish performance.