Probiotic additions affect the biofloc nursery culture of white shrimp (Litopenaeus vannamei)

In a biofloc technology (BFT) system, the bacterial community is crucial for organic matter metabolism and toxic nitrogenous compound recycling. This study evaluated the effects of the addition of either of two commercial probiotics (P1 and P2) on the biofloc condition, water quality, and growth and survival of white shrimp (Litopenaeus vannamei) in indoor BFT systems; indoor BFT systems without the addition of any probiotic was used as the control. The culture density was 150 juvenile shrimp (weight, 0.06 +/- 0.01 g) in 200-L tanks with a culture period of 40 days. The salinity of the culture water was 15 ppt, and molasses was added to the tank for maintaining a C/N ratio of 15. In the P1, P2, and control groups, the floc volume was 3.7 +/- 0.5, 3.5 +/- 0.6, and 3.0 +/- 0.6 mL/L, respectively, and the total heterotrophic bacterium densities were (5.8 +/- 1.4) x 106, (4.5 +/- 1.5) x 106, and (3.6 +/- 1.1) x 106 colony forming unit (CFU)/mL, respectively; these values were significantly higher in the treatment groups than in the control group (all P < 0.05). The major groups in the biofloc comprised zooplankton community were provided by rotifers, copepods, nematodes, and protists. The addition of probiotics increased nitrite-nitrogen and nitrate-nitrogen levels in the culture water of P1 (7.7 +/- 1.0 and 5.9 +/- 0.5 ppm, respectively) and P2 (8.4 +/- 0.7 and 6.2 +/- 0.6 ppm, respectively) groups; they were significantly higher in the treatment groups than in the control group (6.1 +/- 0.8 and 5.0 +/- 0.8 ppm, respectively). L. vannamei growth rates were significantly higher in the P1 group than in the P2 and control groups. However, the between-group differences in the survival rates were not significant. In conclusion, the addition of probiotics to the BFT system with L. vannamei effectively enhanced the water quality, floc volume, and total bacterial number in the water and the growth performance of the shrimp.