Probiotic Applications in Crustaceans - Aquaculture Nutrition: Gut Health, Probiotics and Prebiotics - page 292

the host and therefore the farmer and the final consumer. We will then only consider direct
probiotic effects on the host, which are achieved, in part at least, by improving the microbial
balance of the animal. Nevertheless, as extensive applications exist in shrimp farming, several
references will also be made to microorganisms used as bioremediation agents.
In the past two decades research has been conducted to select probiotic strains and evaluate
their effects on crustaceans, specifically on marine shrimps. Commercial probiotic prepa-
rations, already available for terrestrial animals, have also been evaluated. The constantly
increasing number of studies on this topic has made it possible to achieve first reviews detailing
the various developments made in the use of probiotics in aquatic cultured species, including
crustaceans (Gatesoupe 1999; Verschuere etal. 2000a; Gomez-Gil etal. 2000; Farzanfar 2006;
Balcázar et al. 2006; Wang et al. 2008; Castex 2009; Qi et al. 2009). However, in contrast
to the broad application of probiotics in commercial shrimp farms (hatcheries and grow-out
farms), relatively few in-depth studies on their mechanism of action have been published so
far. Therefore many questions about how probiotics actually work in crustaceans still remain
unanswered. According to the probiotic definition (Fuller 1989; Gatesoupe 1999; Merrifield
et al. 2010), the primary effect of probiotics relies on the modulation of the intestinal micro-
biota of the host. Then, a first question to consider is whether probiotics are actually able to
modify the associated microbiotas of crustaceans. This review will address this fundamental
question and will update the main information presently available on the mechanisms of action
of probiotics in crustaceans.
Even though information on mechanisms is scarce, this chapter will summarize the various
benefits of probiotics in crustacean species reported in many scientific studies and field reports
which have led to probiotics becoming accepted among the scientific communities as well
as the professionals in this sector (e.g. farmers, feed producers, veterinarians). Although the
probiotic concept is gaining momentum, statistical data about the efficacy of probiotics in
commercial farms are scarce and more pilot scale studies are needed to assess the efficacy
of a particular probiotic under farming conditions. Nevertheless, beyond these considerations,
probiotic applications have been a practical and commercial reality in shrimp farming for more
than 10 years, especially in Asia. For instance, Qi et al. (2009) report that more than 100
companies in China are producing various types of probiotics for applications in aquaculture.
The authors estimated that around 50,000 tonnes of commercial probiotic products were sold
annually in China with a market value estimated at €50 million. To a lower extent, and even
if figures are lacking, similar situations can be encountered in other Asiatic countries such as
India and Thailand (Nimrat and Vuthiphandchai 2011), or in South and Central America as
reported for instance in Ecuador (Cedeño 2007; Rodríguez et al. 2007). A survey conducted
by the research Institute CENAIM in Ecuador of over 56 farms showed that 89% of farms
were using probiotics, more than 20 different products were being applied, and in 57% of the
cases the bacterial strains used were of local origin. This scale of commercial development of
probiotics leads therefore to regulatory and industrial issues (refer to Chapter13 ). For instance,
product quality and consistency are very critical issues when it comes to the safety and efficacy
of the products being used by farmers (Wang et al. 2008). A recent report from Thailand
highlighted these particular issues and argued that more attention must be paid to evaluation
of the quality of the commercial probiotics used in commercial shrimp farms (Nimrat and
Vuthiphandchai 2011).