MANAGING BIOFLOCS OPERATIONAL PARAMETERS AND USE OF PROBIOTICS CAN MINIMIZE THE RISK FOR HEPATOPANCREATIC NECROSIS DISEASE (AHPND) OUTBREAKS
Biofloc technology is a mature ecosystem composed by a microbial community. It has been reported to improve water quality, feed utilization and shrimp health. Therefore, biofloc systems are claimed to provide protection against bacterial diseases, and the establishment of such systems can be managed by applying probiotic bacteria which also seems to be an alternative for the control of diseases. In this study, it was tested if bioflocs operated in different ways show a different capacity to control AHPND. Additionally, it was verified if Bacillus-based probiotics would allow to control the disease independently from the operational parameters.
L. vannamei postlarvae (PL22 - 0.025±0.01g) were cultured (30 shrimp/10L tank) for 21 days in five different experimental bioflocs: No bioflocs (clear water); Autotrophic bioflocs (cultured at C/N < 10) with and without probiotic supplementation; and Heterotrophic bioflocs (cultured at C/N >15) with and without probiotic supplementation. The commercial probiotic mixture (Sanolife® PRO-W) was added to the water every 48 hours. At the end of the period, an AHPND challenge test was performed in 3 different methods: A - Shrimp cultured in the bioflocs were challenged in new seawater without bioflocs; B - Shrimp cultured in the bioflocs were challenged in that same biofloc suspension; C - Non-experimental shrimp were challenged in the different biofloc suspensions.
Overall, survival was lowest when shrimp were challenged in new seawater (Fig1A), independently of the biofloc suspension in which the shrimp were cultured before. When challenged in bioflocs, survival was highest in Heterotrophic bioflocs. Survival in Autotrophic bioflocs was lower, but could be compensated by the use of Sanolife® PRO-W (Fig 1B;1C). These effects were independent of whether the shrimp has been cultured before in the bioflocs or not.
These results illustrate the protective effects of bioflocs and that operational parameters of biofloc systems can determine the degree of disease risk. In addition, this study showed the potential of using Sanolife® PRO-W in combination with bioflocs for the case these would not be able to provide protection of the shrimp against AHPND.
