Agriculture Reference
In-Depth Information
optimal feed incorporation conditions. European Commission guidelines for the approval of
feed additives require applicants to provide evidence of the optimal conditions for the incorpo-
ration of the probiotic microorganism in the feed in addition to a demonstration of its stability
over at least a 3 month period.
Protecting viable probiotic cells, that is providing a physical barrier against adverse
environmental conditions, is receiving considerable attention. One could consider, for
example, micro-encapsulation of microbial cells as detailed by Kailasapathy (2002), and
patented micro-encapsulated bacteria or yeasts are currently commercially available (Ziggers
2005; US patent 7157258 B2). Recent improvements with the technology in commercially
available live yeast applications have led to reports where encapsulated products have been
shown to resist temperatures as high as 80-90 C (Ziggers 2005). Despite this, applications
to shrimp feeds or extruded fish feeds are still at an early stage, necessitating approaches
where feed manufacturers are looking internally for options involving optimization of their
processes and/or the equipment used.
Post-pelleting applications, for example by spraying, are generally alternatives that have
shown some promise in terms of homogeneity, stability and conformity at both laboratory
and industrial levels (Ziggers 2010; Lallemand unpublished results). Such applications with
salmon feeds have shown promising results in terms of probiotic survival, including exposure
to harsher pressure, temperature and flow rate, for several months at both laboratory and indus-
trial levels (Ziggers 2005). Significant financial investments are required in order to implement
post-pelleting applications; however, given the increased usage of feed additives (not only
biotics) in aquafeeds, it appears that the use of drum or vacuum coaters, as currently used in
salmonid and/or marine fish feeds in Europe, is here to stay. Nevertheless, for the future of
probiotic development, alliance and transversal experience gained from biological technology
and industrial processing applications should inform innovative and easy to use solutions for
the feed industry.
Administration of probiotics to fish and shrimp via rearing water is also a common practice
which has received much attention. From a technological point of view, probiotics developed
for such applications must be formulated with certain specific features: (1) good stability in
water, (2) float control in the tanks/ponds, and (3) high concentration favouring a low daily
dosage to avoid possible contamination by the carrier (when used in excess, certain carriers
in probiotic formulations can promote undesirable growth of non-beneficial microorganisms
in the tanks/ponds). This entails specifically formulated products. In practice, sophisticated
applications via water have been mainly considered for fish and shrimp hatcheries (larval tanks
and live prey cultures) for obvious practical reasons, while 'bio-remediation' strategies are
mainly implicated in live microorganisms for shrimp and freshwater fish ponds.
There are limited data comparing the effectiveness of water based versus feed based admin-
istration of probiotics to fish and shrimp (Merrifield et al. 2010a). Water application is not a
practical way to supply probiotics in open systems such as flow-through and sea/lake cages,
except if used for bath treatments, which themselves have clear limitations. The development
of recirculating aquaculture systems might of course offer new possibilities; however there
could be regulatory constraints and/or welfare issues that might pose enormous challenges.
As an example, one of the critical factors with water application is the low level of control
over the quantity of probiotics actually ingested by the animal, which may lead to concern
about precision with regards to the minimal/maximal dose of use.
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