Contribution of bioflocs in the diet of shrimp Litopenaeus vannamei during the nursery and fattening phases using the stable isotope technique
The shrimp production technology in the midst of bioflocs (BFT) is considered one of the most suitable and promising for the sustainable development of shrimp farming, allowing for high storage densities of Litopenaeus vannamei, and the use of smaller areas and greater productivity when compared to systems traditional. In order to determine the importance of bioflocs, in recent years the technique of stable isotopes has been applied in research in aquaculture production, and thus this tool has helped in the understanding of which food source overlaps in importance for the cultivated species. From this, this work had the objective to evaluate which is the nutritional contribution of each food present in the system,through the technique of stable isotopes of carbon and nitrogen to determine the influence of bioflocs in post-larvae and juveniles of L. vannamei during the nursery and fattening phases. For this, two experiments were designed with three treatments and four repetitions, distributed in treatment 1: where the shrimp were fed only with food, treatment 2: only bioflocs as a food source and treatment 3: with food based on bioflocs + food. Water quality parameters were monitored daily and the zootechnical performance of the shrimp was monitored by weekly biometrics, and every 15 days samples of feed, bioflocals and shrimp were collected for stable isotope analysis. In addition, the microbial community and chlorophyll levels were analyzed during the experiment. Dissolved oxygen,temperature and salinity did not show significant differences between treatments, while nitrogen compounds showed significant differences between them, and suspended solids and turbidity were higher in biofloc treatments. In the nursery experiment, the growth in the treatment of Bioflocs with feed was lower, when compared to the control treatment, due to the presence of cyanobacteria of the Pseudoanabaenacea family, however the survival was statistically equal in these treatments. In the fattening experiment, growth and survival did not differ statistically between Control and Biofloco treatment with feed, with a final weight of 7.97 ± 2.03 g and 7.69 ± 2.27 g, respectively.To assess the contribution of bioflocs and feed, an isotopic mix model was used to measure the levels of carbon and nitrogen isotopes in the shrimp tissues. Therefore, it was observed that bioflocs can contribute from 22 to 43% in the growth of shrimp 240 during the nursery phase and from 63 to 86% during the fattening phase.