World Aquaculture - December 2014

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36 DECEMBER 2014 • WORLD AQUACULTURE •
Controlling Inflammation
with Flavanoids—An Option
for Future Aquafeeds
Malte Lohölter, Susanne Kirwan and Bernhard Eckel
With annual growth
rates of approximately 10
percent throughout the last five
decades, the global aquaculture
sector is the fastest growing
food-producing industry in the
world (Pettersson 2010). Despite
great past and present success,
aquaculture is facing diverse
challenges, including a need
for increased productivity and
efficiency while simultaneously
implementing further
replacement of traditional feed
ingredients derived frommarine
fisheries. Achieving these
apparently opposite targets will
be ambitious and likely to have
unexpected side-effects that
need to be taken into account in
expedient diet formulation.
Current research indicates
processes subsumed as
inflammation may be among
these detrimental side-effects,
leading to suboptimal feed
efficiency, animal growth
and eventually affecting
profitability of the production
system. The present article
summarizes current knowledge, providing a glimpse at the potential
future impact of inflammation on cultured aquatic species, while
discussing existing and conceivable solutions.
Impacts of Inflammation
Inflammation is often imprecisely considered a synonym
for infection but should be understood as a complex stereotypic
response of the body to damage of its tissues or undesired chemical
(reactive oxidants, acids, lyes, toxins), physical (foreign objects,
radiation, heat, cold) and biological (viruses, bacteria) stimuli
(Weiss 2008). The main objective of the processes subsumed as
inflammation is to eliminate the damage, stop the spread of injury
and restore the functionality of the affected regions.
The body responds to the onset of inflammation with molecular
changes in gene expression and diverse reactions of the immune
system. In the initial reaction, affected tissues are subjected to an
increased blood flow, followed by altered concentrations of different
plasma proteins and white
blood cells. The liver responds
with increased production of
specific proteins (so-called
acute-phase proteins) that
are capable of destroying
or inhibiting microbes and
subsequently giving a negative
feedback to the inflammatory
response to down-regulate the
physiological response to the
stimuli. At the molecular level,
inflammatory processes are
regulated by a protein complex,
NF-ĸB, which is found in its
inactive form in the liquid
phase of cells. As summarized
in Figure 1, inflammation can
ultimately lead to impaired
liver function, anorexia, pain
and muscle degradation.
But what happens if the
defense mechanisms of the
organism are not able to fully
limit the inflammation to its
transient acute form (lack of
healing)? So-called chronic
inflammation can occur and
lead to the development of
a variety of disorders. In
contrast to acute inflammation, which is typically characterized by
the five signs of pain, heat, redness, swelling and loss of function,
chronic inflammation is often less visible and can affect apparently
healthy animals, which are well supplied with all required nutrients,
according to current recommendations. In humans, chronic
inflammation is known to be related to cancer, allergic reactions,
atherosclerosis and myopathies. As a general consequence of
inflammation, the physiological priority is shifted toward healing
and cell protection, meaning that a considerable amount of dietary
energy and protein is used to control these processes and is no
longer available for tissue and muscle growth. Thus, animals are no
longer able to reach their genetic potential and farmers are likely to
experience economic losses.
The Future Situation
Production losses associated with inflammation are likely to
increase in future aquaculture. Although knowledge and awareness
TOP, FIGURE 1.Physiological effects related to inflammation. BOTTOM,
FIGURE 2. Dietary inclusion of fishmeal in aquafeeds from 1995 to 2010 (Redrawn
from Tacon et al. 2011).