Contribution of diatoms and artificial substrates to bioflocs and performance of Litopenaeus vannamei juveniles grown in BFT system
Aquaculture is the fastest growing animal production activity in the world and shrimp farming has a high commercial value. Technological advances have allowed the development of a super-intensive cultivation system without water renewal in the presence of bioflocs, called the BFT system (Biofloc Technology). This system has great advantages, as it reduces the emission of effluents through the reuse of water for several production cycles, reducing the risks of spreading diseases and providing nutritional benefits. The microbiota contributes to the maintenance of water quality and serves as a supplementary food for cultivated animals. In this work, the influence of the presence of diatoms (Amphora coffeaeformis Cylindrotheca closterium,Conticribra weissflogii) and artificial substrate in the formation and nutritional quality of bioflocs and in the performance of shrimp Litopeneaus vannamei (Boone, 1931) grown in BFT. The experiments were carried out in rectangular tanks (0.5 m2; 200 L) inside the greenhouse in order to (1) evaluate the contribution of diatoms to the formation of bioflocs and growth performance of juvenile shrimp in BFT; (2) test whether the selection of diatom species can improve the growth performance of juvenile shrimp in BFT; and (3) to compare the effect of adding diatoms and artificial substrate in BFT on the growth performance of this shrimp. It was found that the maintenance of diatoms in high cell density requires the addition of silica and contributes to the performance of the shrimp.The addition of Amphora coffeaeformis and Conticribra weissflogii resulted in better shrimp growth, which showed high survival rates, weight gain, final average biomass and efficient feed conversion. The levels of lipids (2.64 to 5.11%) include essential fatty acids, especially linoleic acid (C 18:02) and eicosapentanoic acid (EPA) (C 20:05 n3). The presence of diatoms was more important than the use of artificial substrates to improve the growth performance of L. vannamei shrimp. In summary, the results obtained help to improve the BFT, and indicate that the addition of silica is necessary to maintain the presence of high density diatoms. The selection of diatom species is important for your own best shrimp growth and performance. Lastly,it is highlighted that the addition of diatoms is more important than the artificial substrate, aiming at a better efficiency and performance in a biofloc cultivation system.