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Modulation of fish larval defence mechanisms by immunostimulants

- Carp.
Adding immunostimulants to carp larval diets did not induce significant gene expressions (IL-1beta, TNF alpha and iNOS, C3, alpha-2-macroglobulin and SAA), whereas the contents of B cells, evaluated using flow cytometric analysis, in immunostimulated carp was lower compared to controls. Taken together, it appears that some immunostimulants affect leucocyte numbers and dynamics, whereas it is difficult to compared such effects with increase in gene expression of the selected genes.

- Sea bass.
The alginate (FMI) supplied by the project¿s co-ordinator, when administered by bathing or orally resulted in an apparent better growth of animals, although it not affected the cellular and molecular parameters studied.

The A. salmonicida LPS had a detectable and reproducible physiological effect when administered orally to sea bass, and this effect did not affected larval viability and cellular and molecular parameters studied. In sea bass, LPS induced immunostimulant that appeared to be the most effective without any pathogen challenge.

- Atlantic cod.
So far, it seems that the immunostimulants in question did not induce disease resistance, elevated cellular defence mechanisms or humoral defence mechanisms. However, more work is required and is indeed in progress to evaluate the effects of immunostimulants.

- Atlantic halibut.
Difficult to interpret the results

- Spotted wolffish.
The addition of bioactive alginate in formulated feed induced higher specific growth rate compared to controls. No significant disease resistance was observed in immunostimulated fish. The use of immunostimulants as growth promoters may have high impact on the mass production of fish juveniles. Bioactive alginate is currently under investigation as a feed additive for use in several other fish species.

Related information

Reported by

University of Tromsø
Department of Marine Biotechnology, Norwegian College of Fishery Science
N-9037 Tromsoe
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