Influence of wheat and rice bran fermentation on water quality, growth performance, and health status of Common carp (Cyprinus carpio L.) juveniles in a biofloc-based system

Abstract

The present study was aimed to compare the effect of wheat and rice bran fermented with probiotics (Bacillus coagulants, Bacillus subtilis) on liver and intestine histology of Common carp. Additionally, its effect on water quality, growth performance, hemato-serological indices and oxidative stress in biofloc based system for Common carp juveniles was investigated. To compare fermented (FWB + BFT: fermented wheat bran, FRB+BFT: fermented rice bran) and non-fermented (WB + BFT: wheat bran, RB + BFT: rice bran) treatments, 375 healthy juveniles (25.1 ± 1.6 g) were randomly distributed in 12 tanks (70 L). In the fermented treatments, wheat and rice bran were pre-fermented for 24 h, and then added to the culture tanks and in control. No carbon source was added while 30% of the water was changed on a daily basis. After 60 days, the results revealed that total ammonia nitrogen, pH, biofloc floc volume, and dissolved oxygen decreased in the fermented sources compared with those of the non-fermented treatments. Moreover, the results indicated that fermentation improved growth performances, and the highest significant weight gain and protein efficiency ratio, along with the lowest feed conversion ratio and feed intake belonged to FWB + BFT, which was different with non-fermented brans (P < 0.05). The fish reared in FWB + BFT had a significantly higher total protease, amylase, and lipase activity than those in the non-fermented groups (P < 0.05). A significantly higher body protein was seen in the fermented treatments (P < 0.05), while due to high lipid content in rice bran, the highest body lipid content was observed in the rice bran treatments. In comparison with non-fermented treatments, the most sero-immunological parameters improved in FWB + BFT group and significant difference was seen (P < 0.05). The experimental treatments affected the antioxidant enzymes, and the highest superoxide dismutase and glutathione peroxidase as well as the lowest malondialdehyde were observed in the fermented groups, which was different with the non-fermented treatments (P < 0.05). Histological changes were found in the juveniles intestine, and mucosal layer quantification and qualification than the fermented groups significantly improved in comparison with those in non-fermented treatments (P < 0.05). Overall, the result of this experiment revealed that fermentation of complex carbon resources improves water quality and increases growth performance and health status in the biofloc system.