The management of shrimp health is a prerequisite for sustainable and profitable farming. Emergence of pathogens, global transfers and associated epidemic mortalities have plagued shrimp producers for decades. Controlling highly virulent vibrio infections remains an ongoing struggle. Successful management of disease depends upon the concurrent application of several strategies. First, the use of pathogen free and disease tolerant seed stocks. Second, maintaining a wholesome environment that does not favor disease proliferation. Third, the application of advanced feeds which contribute directly to a robust and healthy target crop.
Many of the disease problems facing the industry can be traced to biosecurity lapses in the hatcheries. In many places, hatcheries make great investments in disease free broodstock. Unfortunately, the health of the seed stock at the end of the production process can often be compromised by pathogens which are introduced and or proliferate during maturation, spawning and larval culture. Current hatchery feeding practices are characterized by the use of natural feeds. Polychaetes, squid, bivalves, Artemia biomass, and krill are staples of the maturation diet, while live microalgae and artemia nauplii are major components of the larval diet. However, there is increasing evidence that many of these natural feeds contribute to subsequent disease problems in hatcheries and farms. Polychaetes are a particularly risky vector for introduction of disease. Algae cultures have been implicated in outbreaks of Zoea II syndrome and Artemia nauplii hatching systems are notorious as sources of pathogenic Vibrio.
Advancements in the development of specialty feeds for hatchery applications are the subject of intense research and development efforts. While no commercial maturation diet has been developed yet that is capable of replacing 100% of the natural maturation feeds with no decline in fecundity, new maturation diets on the market have been demonstrated to successfully replace 100% of frozen polychaetes. Replacing the riskiest components of the maturation diet can pay dividends in reduced bacterial loading and improved survival of the nauplii in larval rearing. Many hatcheries have successfully replaced 100% of Artemia nauplii with commercially formulated replacement diets that match or exceed the nutritional composition of Artemia. Complete and partial replacement has been demonstrated to reduce Vibrio counts in the water and in the larvae. New advanced diets contain health additives which improve digestive health and fitness while reducing gut pathogen levels for all stages of the maturation, hatchery and nursery cycle. Functional probiotics can play an important role in improving health directly in the shrimp and in the culture system. Introduction and proliferation of pathogens in the hatchery causes tremendous economic losses for shrimp farms. In an increasingly competitive shrimp market, the most profitable farms will be those that understand the value of investing in robust high-quality seed stock, challenging feed providers and hatchery managers to continual improvement of feeding and husbandry practices.