Investigating health management strategies in Thai shrimp hatcheries

Abstract

Marine shrimp like Penaeid are one of the most important farmed species which provide an economically valuable seafood product in Thailand. However, infectious disease outbreaks continue to be a serious issue that results in production losses. To support the grow-out farmers, who rely on the good quality of hatchery reared seed, the shrimp larvae supplies from the hatcheries must be healthy and pathogen free to ensure good growth rate and a high value product in the grow-out section. Health management is an important aspect of ensuring that the sector remains buoyant and can produce high quality of post larvae (pl).

One of the findings from the hatchery survey data of this study found that control of temperature in larger tanks gave a statistically significant survival rate in the pl shrimp (P≤0.05) compared with those without temperature control and using small scale tanks. Controlling temperature with larger tanks as well as probiotic supplementation are recommended for the Thai hatchery section. Furthermore, from the survey data, there was a high level of use of probiotics by many of the Thai shrimp hatcheries. A study was performed to investigate the effect of probiotic on the health of the marine shrimp. The results of this experimental study found that administration of a single probiotic substance containing the Gram positive Bacillus licheniformis gave a statistically significant higher level of survival (P≤0.05) compared with shrimp in the control group. The probiotic was fed to the shrimp via live artemia at a concentration of 10^6 cfu per ml. While no other statistically significant changes were identified between the shrimp fed the probiotic and the control group, it was important to note that administration of the probiotic did not cause any negative side effects.

A further experimental study was performed to evaluate if the probiotic fed shrimp were less susceptible to pathogenic strains of Vibrio parahaemolyticus which caused Acute Hepatopancreas Necrosis Diseases (AHPND). Two strains of V. parahaemolyticus were included in the study and these were administered to the shrimp by static bath. The results of the bacterial challenge study showed that for

both V. parahaemolyticus strains less mortalities occurred in the shrimp groups administered the probiotic before challenge. There appeared to be a bacterial concentration effect of the V. parahaemolyticus strains as the highest cumulative mortality was found in the shrimp group receiving the highest bacterial concentration. Overall the experimental bacterial challenge studies suggested that there was a trend for the shrimp receiving the probiotic to be associated with less AHPND.

In conclusion, this study used a mixture of methods in order to improve our understanding of health management strategies in Thai marine shrimp hatcheries. The data provided evidence that temperature control in larger size tanks gave improved survival of the shrimp. Under experimental conditions, administration of probiotics could be beneficial to reduce bacterial infection from AHPND-causing V. parahaemolyticus, as well as improving of survival rate. The research performed has generated new knowledge on improvements in health management in Thai shrimp hatcheries and has provided the foundation for future studies to explore the mechanistic effect of probiotics within these systems.