In the biofloc system, the potential of carbon sources may include simple ones such as molasses, glycerol and glucose, and complex ones such as flours and starches. Different carbon sources result in different nutritional values of the biofloc. In addition, they have varying effects on the composition of the microbial community in the biofloc, the production, and the immunity of the cultured shrimp. The addition of different carbon sources effectively increases the growth of microorganisms (bacteria, protozoa, algae and zooplankton), which could be attributed to the higher densities of bacteria in the biofloc system. So, the biofloc system could serve as an important food source without the need to add feed or external diets, and thus increase the growth of shrimp.
A 90-day out-door growth trial was conducted to evaluate the influence of using different carbon sources on nutrient utilization efficiency in biofloc system on the digestive enzymes in both stomach and intestine of Litopenaeus vannamei post-larvae (0.02±0.01g). Both sugarcane bagasse (SCB) and rice straw (RS) were used as an organic carbon sources that were added into the tanks to promote the development of biofloc as a natural feed during the experiment. During the entire experiment, good water quality and biofloc development were achieved under the addition of different carbon sources. Overall, the specific activities of protease, amylase, lipase and cellulase in both stomach and intestine of L. vannamei shrimp in biofloc treated group were significantly improved (Figures 1 & 2) when compared with control one (P < 0.05).
Acknowledgements: The research was performed within the "EGY-DRAFT" project (Development and Research Application of bioFloc Technology for increasing shrimp production in Egypt), funded by the Science, Technology & Innovation Funding Authority (STDF), Egypt. Agreement No.: 25305/Reintegration Grants (STDF-RG)/STDF-Youth. The authors are grateful for all the support.