The effect of different carbon sources on bacterial count and histometric of Cyprinus carpio intestine, reared in a biofloc system

In this study, effect of different carbon sources (carrot pomace and molasses) on total bacterial count and histology of intestine in Cyprinus carpio, reared in a biofloc system was investigated. 243 fish (16.8±2.1g BW) were purchased and randomly distributed in 50-liter aquarium (9/aquarium) for 8 weeks. Nine different treatments, including a treatment with 100 % daily feeding rate (3% BW) with water exchange as a control, the other 8 treatments were assigned to biofloc systems, including treatment 2 (100%), 3 (75%), 4 (50%) and 5 (25%) daily feeding rate in addition to carbon source carrot pomace and 4 other treatments, including treatment 6 (100 %), 7 (75%), 8 (50%) and 9 (25%) daily feeding rate in addition to carbon source molasses. At the end of experiment, total number of bacteria in the aquaria water and intestine of each fish was counted. Additionally, intestine histology was investigated using H&E. The results showed that there are significant differences in bactria counts of intestine and water between biofloc treatments and control. The highest number of intestinal bacteria (7.7±0.008 logCFU/g) was related to treatment 5 and the least of that was observed in control (6.08±0.018 logCFU/g). The highest number of bacteria in water media (6.18±0.023 logCFU /ml) was obtained in treatment6 and the least of that was related to the control (4.18±0.03 logCFU/ml). Significant (p<0.05) increase in villi length was observed in treatment 3. The biofloc system and the addition of carbon source caused changes in bacterial count of intestine and water culture media besides alterations in villi length, club shaped cells and leukocytes of carp intestinal.