The effect of vitamin C on fish health
DSM Nutritional Products
Viviane
Verlhac and Jacques Gabaudan Centre for Research in Animal Nutrition,
Société Chimique Roche, BP 170, 68305 Saint-Louis Cedex, France
The
goals of the aquaculture industry are to optimize growth and to produce
high-quality fish. As in all farming, the outbreak of diseases in fish
farming can be a major concern. The high susceptibility of fish to
stress and the rapid spread of diseases in water have forced
aquaculturists to concentrate their efforts on maintaining their fish
in good health in order to achieve sustainable economic performances.
Growing
healthy fish requires them to be able to develop strong defence
mechanisms against pathogen invasion. These are the non-specific and
the specific immune response. The non-specific immune response is more
important in fish than it is in mammals. Improving the immune response
leads to a better vaccination efficiency. Vaccines induce a specific
immune response and an increased capacity to kill the pathogens by
non-specific defence mechanisms.
Several
years ago, during the early development of the salmon industry,
antibiotics were commonly used in the treatment of diseases. However,
the consumption of drugs has progressively been reduced owing in part
to environmental and regulatory concerns and in part to increased
resistance of pathogens. Furthermore, the curative effect of oral drugs
is minimised by the fact that diseased fish frequently do not feed. The
eradication of major diseases by improved husbandry and vaccination has
reduced mortality levels considerably. Although some efficient vaccines
against major diseases of finfish are available today, others need to
be improved in terms of efficiency and duration of protection. Vaccines
against lethal diseases such as VHS and BKD have not yet been developed.
Intensively
raised fish may be exposed to stressful situations which often result
in a depressed immune status. Good management practices reduce stress
and therefore help to maintain healthy animals. However, since not all
stressing situations can be avoided, fish with enhanced defence
mechanisms will be better prepared to combat the negative effects of
stress. The nutritional quality of the feed is a major factor in
sustaining healthy fish. It has been shown that the immune system can
be enhanced by the use of immunomodulators such as antioxidant
vitamins, carotenoids and other feed additives. The combination of good
management, vaccination and nutritional prophylaxis will insure higher
survival rates and improve growth in intensive farming systems (Figure
1).
This
publication highlights the importance of vitamin C as an
immunomodulator and a key nutritional element in modern fish farming in
promoting optimal survival and performance.
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