Examination of the immunomodulatory properties and the effect on disease resistance of dietary bovine lactoferrin and vitamin C fed to Atlantic salmon (Salmo salar) for a short-term period

Atlantic salmon were fed commercial diets with or without supplementation of 140 mg bovine lactoferrin (Lf) kg(-1) feed, and with 150 or 1000 mg vitamin C (ascrobic acid, AA) equivalents kg(-1) feed using AA polyphosphate, in a 22-factorial design for 19 days. Following the dietary treatment the experimental fish were challenged with Aeromonas salmonicida ssp. salmonicida or infectious salmon anaemia (ISA) virus. The specific growth rates were unaffected by the dietary treatments. Liver AA concentration was increased in all dietary groups demonstrating that the fish had been eating. Liver iron and head kidney catalase did not differ significantly between the groups. Lysozyme activity in serum and head kidney, spontaneous and antibody specific serum complement-mediated haemolysis as well as phagocytic chemiluminescent responses were all unaffected by the differences in dietary composition. In the furunculosis and ISA challenge experiments there were no significant differences in cumulative mortality between the groups. In conclusion, under the experimental conditions used in this study we were not able to detect any effects on non-specific immunity or disease resistance after feeding Atlantic salmon Lf and/or AA supplemented diets for a short period, but masking of potential effects due to low water temperature (8.4 degrees C) and limited feed intake cannot be excluded. (C) 1999 Academic Press.