Effect of Adding Leftover Bread to Iraqi Restaurant Waste on the Common carp (Cyprinus carpio) Diets and its Impact on Growth and Chemical Composition

In this study, five diets were prepared using dry bread residues from popular Iraqi restaurants. The leftover bread (LB) was used at percentages of 0, 0.5, 2, and 3% for a period of 72 days in feeding the common carp (Cyprinus carpio)  fish. The study was conducted to assess the effect of the leftover bread (LB) in fish diets and their impact on growth indicators, feed utilization, and fish body composition chemically. The experiment was designed with five treatments and three replicates, with 9 fish allocated to each treatment. Significantly superior results (P≤ 0.05) were observed for final weight (FW), weight gain (WG), and daily weight gain (WGD) for the treatment (LB 2%). The highest final weight was recorded in the LB 2% treatment (50.78±0.42 gram). The results of weight gain (WG) and daily weight gain (WGD) were significantly higher for the (LB 2%) treatment, recording 40.34±0.34 and 0.55±0.003gram, respectively. Treatments (LB 2%) and (LB 3%) outperformed significantly (P≤ 0.05) in the feed conversion ratio (FCR) efficiency, giving values of 2.36±0.12 and 2.35±0.05, respectively. The feed conversion efficiency percentage (FCE%) for the LB 2% treatment (44.48±0.00) was significantly higher than the other treatments. Both the specific growth ratio (SGR %) and relative growth ratio (RGR %) significantly outperformed (P≤ 0.05) in the (LB 2%) treatment compared to other treatments, recording 2.19±0.005 for SGR % and 386.70±0.01 for RGR %. The protein efficiency ratio (RER) was significantly higher (P≤ 0.05) in treatments (LB 2% and LB 3%), recording (1.62±0.000 and 1.64±0.02), respectively. The chemical analysis of fish bodies indicated that the protein content in fish bodies significantly surpassed (P ≤ 0.05) in treatments LB 2% and LB 3% compared to the other treatments, recording (70.85±0.6) and (69.47±0.07), respectively. The results also showed that the fat content in fish bodies in the experimental groups significantly exceeded (P≤ 0.05) in treatments LB 0.5%, LB 1%, and LB 3% compared to the other treatments. The significance of this study lies in determining the optimal utilization of bread residues in fish diets and reduce the disposal of dry bread as waste, with reassuring results by adding 2% of dry bread to the diets.