Influence of combined vitamins C and E on non-specific immunity and disease resistance of rainbow trout, Oncorhynchus mykiss (Walbaum)

The effect of various combinations of vitamins C and E on immune response a nd disease resistance was investigated in rainbow trout, Oncorhynchus mykis s (Walbaum). The following combinations of vitamins were included in the di et (C/E): 0/0, 0/800, 2000/0, 30/30, 30/800, 2000/30, 2000/800. Liver ascor bic acid and alpha-tocopherol contents reflected the dietary treatments wel l. Complement levels showed no significant differences. The combination of the high dietary doses of vitamins C and E significantly stimulated lymphop roliferation induced by Concanavalin A when compared with fish fed a low le vel of both vitamins, but also when compared with fish fed a low level of v itamin C and a high level of vitamin E. The highest macrophage oxidative bu rst activity, measured by chemiluminescence, was found in fish receiving bo th vitamins at high levels. In the disease resistance experiments, the best survival rates in trout infected with viral haemorrhagic septicaemia virus were achieved with diets containing both vitamins at a high level, or at l east one at a high and the other at a low level. Highest mortalities in fis h infected with Yersinia ruckeri occurred in trout fed double-deficient or double low diets. The best survival of fish exposed to Ichthyophthirius mul tifiliis was achieved with diets high in one and low in the other, or high in both vitamins. However, differences were not statistically significant i n the parasite experiment.