Effect of different frequencies of the addition of Brachionus plicatilis on the performance of Litopenaeus vannamei in a nursery biofloc system with rice bran (anaerobic and aerobic) as an organic carbon source

Abstract

The aim of the present study was to evaluate the effect of different frequencies of the addition of the rotifer Brachionus plicatilis on growth, water quality, plankton composition, Vibrio, Bacillus and fungi (filamentous and yeast) in a nursery biofloc system with rice bran (anaerobic and aerobic) as an organic carbon source for Litopenaeus vannamei. Four treatments were used: BFT (biofloc without addition B. plicatilis); BFT-1F (addition of 30 org mL−1 of B. plicatilis on the 1st day); BFT-2F (addition of 30 org mL−1 of B. plicatilis on the 1st and 10th days) and BFT-4F (addition of 30 org mL−1 of B. plicatilis on the 1st, 10th, 20th and 30th days). The shrimp (PL10 3.0 ± 0.02 mg) were stocked at a density of 3000 m−3 and fed a commercial feed (45% crude protein and 9.5% lipids). The biofloc system was fertilized every three days for 42 days with anaerobic and aerobic rice bran processes using a microbial mix (0.1 g m−3) with 6.5 × 107 CFUs g−1 of Bacillus subtilis, 2.1 × 107 CFUs g−1 of B. licheniformis and 3.7 × 107 CFUs g−1 of Bacillus strains. The BFT-4F treatment led to higher (p < 0.05) final weight (0.73 g), yield (1.88 kg m−3) and specific growth rate (14.31% day−1). No significant differences (p ≥ 0.05) in water quality parameters were found among the four treatments. The main plankton groups were Chlorophyta and Protozoa. Microbiological analysis revealed an increase in the amounts of Bacillus sp. and percentage of yeast as well as a decrease in the percentage of non-sucrose-fermenting Gram-negative bacteria and filamentous fungi at the end of the experiment compared to the initial culture in both the water and shrimp samples for all treatments. The addition of rotifers four times to nursery biofloc system led to better performance variables, indicating the benefit of these organisms as a natural food source for L.vannamei postlarvae.