Efeito de probiótico comercial sobre o desempenho de pós-larvas de Litopenaeus vannamei em sistema de biofloco e sua influência sobre as comunidades bacteriana e fitoplanctônica

Abstract

The addition of probiotics in shrimp farms has increased as alternative to use of antibiotics and because the demand for more environment-friendly aquaculture. They have been found to improve host performance and health and water and soil qualities, acting as biocontrol and bioremediation agents in the culture systems. The present study investigated the probiotic effects in water quality, shrimp performance, phytoplankton and bacterial community in intensive nursery system with biofloc for the shrimp Litopenaeus vannamei. Tanks were stocked with post-larvae (PL10) at a density of 2100 PL m-3 and initial weight of 2 mg. Commercial probiotic consisted of Bacillus subtilis and Bacillus licheniformis. Treatments consisted of four different concentrations of probiotic: 1) P0.5 (0,5 g/m³ – 2,5 x 107 UFC/L); 2) P1.0 (1 g/m³ – 5 x 107 UFC/L); 3) P2.0 (2 g/m³ – 108 UFC/L); 4) P3.0 (3 g/m³ – 1,5 x 108 UFC/L); and 5) CTL (control - without probiotic). Shrimps presented final weight ranging from 465 to 625 mg, survival from 68.8 to 89.9%, specific growth rate from 8.9 to 9.4% / day, yield from 1.01 to 1.21 kg m-3 and feed conversion rate of 1.2 to 1.6. However, the application of the probiotic did not interfere any of these variables and also did not affect water quality, the composition of phytoplankton and bacteria, without showing significant differences between treatments (P 0.05), except for autotrophic bacteria (P<0.05). Bacteria naturally present in biofloc showed to be sufficient to maintain the culture system balance.