Agriculture Reference
In-Depth Information
The diminishment of natural stocks, the increasing cost of fishing wild shrimps and the
current increase in demand for aquatic products directly favours the development of shrimp
aquaculture. As an example, the farming of white shrimp ( Litopenaeus vannamei ) originating
from the Pacific east coast is rapidly growing worldwide; from 2002 to 2010, the production of
this species rose from 200,000 to 600,000 tonnes in Thailand (Wyban 2007; FAO 2011). The
remarkable growth achieved in the shrimp farming industry over the last 30 years has been
made possible thanks to the intensification and globalization of the seafood trade. However,
the increase in productivity has been accompanied by increased risk of exposure to stress-
ful conditions together with the emergence of several diseases. In fact, disease was rated the
most important issue (coming before production cost of feed and fishmeal availability) for the
shrimp aquaculture industry in the survey by the Global Outlook for Aquaculture Leadership in
2011 (Valderrama and Anderson 2011). Indeed viral and bacterial diseases have posed a seri-
ous challenge for the shrimp farming industry for almost two decades (Bondad-Resantaso etal .
2005). As an example, the recently identified infectious myonecrosis virus (IMNV) in Penaeus
vannamei has caused direct economic losses of US$0.2 billion to $1 billion to the shrimp indus-
try in Indonesia since its first appearance in East Java in 2006 (Sunarto and Sutanto 2011).
More generally, according to the FAO, monetary losses could range from national-level esti-
mates of US$17.5 million to $650 million depending on the outbreak episode, and the global
estimate is US$3.2 billion (FAO 2011). Disease not only affects the sector in socio-economic
terms (losses in income, employment, market access or market share, investment and con-
sumer confidence, food shortages and closure of businesses) but also limits its development
and sustainability (with impacts on costs, trade and biodiversity).
The control and prevention of diseases, especially those of bacterial origin, have been histor-
ically achieved through the use of chemicals such as antimicrobial agents. Antibiotic products
were also used for their growth promoting effect. However, due to the lack of sustainability
and health concerns over the use of such chemicals, their use is today becoming increasingly
restricted by governmental policies, certification programmes and farmers' organizations. It
seems obvious today that the emergence of new pathogens and bacterial resistance was the
result of hazardous management practices. Improving farming practices as well as increasing
product quality to meet consumers' preferences constitute some of the main challenges that
the industry is facing. This will become possible thanks to the development of better man-
agement practices (BMPs) in aquaculture in order to help farmers manage health and food
safety. Such practices are now being implemented in several countries with success and are
seen as the basis for application of GAP and HACCP schemes in aquaculture (Subasinghe and
Ababouch 2009).
Among these practices, the management of microbial communities within aquaculture sys-
tems is gaining momentum and is likely to become one of the most promising areas of progress,
especially since it is now understood that the delicate microbial balance within the digestive
tract and the surrounding environment have a huge effect on the immune system, nutrition and
other physiological aspects of aquatic animals. The use of probiotics as 'biofriendly agents'
to better manage the health of the host and its resistance to diseases and/or to favour growth
and feed utilization through a variety of mechanisms is now a tool increasingly implemented
in farmers' BMPs, specifically in crustacean aquaculture.
For the purpose of the current review it is important to define what we mean here by using
the broad term 'probiotic'. As proposed elsewhere (Merrifield et al . 2010), we will suppose
here that a probiotic is any microbial cell provided via the diet or rearing water that benefits
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