Oral administration of
lipopolysaccharide to Atlantic salmon (Salmo salar L.) fry. Uptake,
distribution, influence on growth and immune stimulation
A. Guttvik, B. Paulsen, R.A. Dalmo, S. Espelid, V.
Lund, J. Bøgwald-2002
Aquaculture, 214(1-4): 35-53
Abstract:
Atlantic salmon fry were fed Aeromonas salmonicida
lipopolysaccharide (LPS)-coated feed for 62 days and then challenged with
virulent A. salmonicida bacteria. The fry were fed LPS-coated feed
also after challenge. Fry that were fed LPS feed (0.1% LPS) showed a higher
mortality throughout the challenge period (accumulated mortality of 57%
after 42 days) compared with fry fed control feed (accumulated mortality of
36.5% after 42 days). Fry receiving LPS-coated feed showed an increase in
mean weight of 10.7% at day 62 compared with fry receiving control feed. The
increase was, however, not statistically significant. Sixty days of feeding
with LPS-coated feed did not result in measurable amounts of specific
antibodies against A. salmonicida LPS in the homogenised fry. The
total amount of immunoglobulins (Igs) was, however, slightly increased.
Studies of immunohistochemical localisation and radioactive LPS distribution
revealed high levels of LPS in the intestinal epithelial cells. Head kidney,
liver and heart showed low levels of radioactivity and no
immunohistochemical staining. In another set of experiments, Atlantic salmon
fry were fed LPS-coated feed (0.03% and 0.01%, respectively) for 64 days and
then challenged with A. salmonicida and Vibrio anguillarum.
The accumulated mortality in fry challenged with A. salmonicida was
40.9%, 34.3% and 30.8% after feeding 0.03% and 0.01% LPS and control feed,
respectively. The accumulated mortality in fry challenged with V.
anguillarum was 47.0%, 55.0% and 55.1% after feeding 0.03% and 0.01% LPS
and control feed, respectively. Fry receiving 0.03% and 0.01% LPS-coated
feed showed a statistically significant increase in mean weight at day 64
compared with fry receiving control feed.
(The Norwegian College of Fishery Science, University
of Tromsø, Breivika, N-9037, Tromsø, Norway, e-mail of J. Bøgwald: jarlb@nfh.uit.no)