Dietary vitamin E and the response of rainbow trout, Oncorhynchus mykiss (Walbaum), to infection with Yersinia ruckeri

Abstract

Rainbow trout fed diets containing 7.86 or 806 mg vitamin E kg-' for 22 weeks were exposed to virulent Yersiniu ruckeri by bath or injection. Mortalities were always least among those fed the highest concentration of vitamin E but serum antibody production was not affected by vitamin E levels.The relationship between diet and the immune response of fish is a topic of increasing interest (Landolt, 1989). Some attention has already been directed at vitamin E, an essential dietary component whose biological activity is principally associated with a-tocopherol. Blazer & Wolke (1984) found that rainbow trout fed diets deficient in a-tocopherol had reduced responses for both specific and non-specific resistance factors but Lall ct al. (1988) reported that diets low in vitamin E did not affect mortality rates or non-specific resistance to furunculosis in Atlantic salmon. Hardie et al. (1990), also working with Atlantic salmon, found that depleted fish had increased mortality rates when challenged with a virulent strain of Aeromonas salmonicida, but from a range of immunological tests, the only significant effect was a reduction in complement activity. The role of dietary vitamin E in disease resistance in salmonids is still not clearly established. Our objective therefore was to induce vitamin E deficiency in rainbow trout and examine the effect on resistance to the enteric redmouth (ERM) pathogen Yersinia ruckeri, compared with fish fed higher doses of the vitamin. Serum antibody titres were measured as indicators of immunocompetence.All female rainbow trout (Oncorhynchus mykiss, Walbaum) weighing 2.5 g, from an ERM-free hatchery, were reared in dechlorinated mains water at 13" C. They were fed on one of three diets prepared (Cowey et al., 1975) with the composition given in Table 1. This basal diet contained 7 mg vitamin E kg ' and the others were supplemented with 86 or 806 mg vitamin E kg-' to provide levels equivalent to commercial diets and megadose levels respectively. Diets, freshly prepared every 3 weeks and stored at -20" C, were fed at 20 g kg ~ I biomass day-I, given in four daily feeds. Vitamin E concentrations were measured by HPLC (McMurray et al., 1980) after extraction from the liver (Bieri, 1969) and diets (McMurray et al., 1980). Liver vitamin C (McGown et al., 1982), erythrocyte fragility and plasma pyruvate kinase (Bell et al., 1985) were measured. Histological examinations were made on 5 pm paraffin wax sections of liver, spleen and skeletal muscle stained with haematoxylin and eosin, and Perl's Prussian blue and Schmorl's reaction identified haemosiderin and lipofuscin. Y . ruckeri (FDL, Weymouth, ref. 13/86) used for challenge,

Low vitamin E in diet reduces stress resistance of gilthead seabream (Sparus aurata) juveniles

“…This is in agreement LOW VITAMIN E IN GILTHEAD SEABREAM with Blazer (1982), who observed no alterations in the growth of rainbow trout fed a non-vitamin E supplemented diet for 4 months when compared with trout fed a diet containing 400 mg of alpha-tocopherol kg 1 of diet. Similar results have been found for species such as Atlantic salmon (Hardie et al, 1990;Raynard et al, 1991), coho salmon (Oncorhynchus kisutch) (Forster et al, 1988), rainbow trout (Blazer & Wolke, 1984;Furones et al, 1992), catfish (Bai & Gatlin, 1993) or seabass (Dicentrarchus labrax) (Stephan et al, 1993). However, other authors have demonstrated the e#ects of vitamin E deficient diets on growth and survival for di#erent species, such as Atlantic salmon (Hamre et al, 1994), rainbow trout (Cowey et al, 1984), chinook salmon (Thorarinsson et al, 1994) and hybrid striped bass (Morone chrysops female Morone saxatilis male) (Kocabas & Gatlin, 1999).…”

“…Erythrocyte fragility, measured as spontaneous haemolysis, was significantly higher in fish fed low levels of vitamin E in the diet at either stocking density. An increase in haemolysis has been widely used as an indicator of vitamin E deficiency (Cowey et al, 1981;Moccia et al, 1984;Wilson et al, 1984) and vitamin E deficiencies caused erythrocyte fragility in several fish species, including rainbow trout (Furones et al, 1992), catfish (Wise et al, 1993a), seabass (Obach et al, 1993) and Atlantic salmon (Hamre et al, 1994). In vitro studies on rat tissues have demonstrated that alpha-tocopherol diminished oxidation of fatty acids (Sen et al, 1997).…”

The effect of dietary immunomodulation upon Edwardsiella tarda vaccination in healthy and immunocompromised Indian major carp (Labeo rohita)

“…Waagbo et al [45] also observed increased survival in vaccinated presmolt Atlantic salmon fed high levels of vitamin C after challenge with A. salmonicida. The positive influence of vitamin E on disease resistance has also been described earlier in many fish species [46,73,74]. However, controversial reports on the e#ect of vitamins C and E on protection have also been described [43,46,73,[75][76][77][78].…”

Performance and hematology of pacu fed diets supplemented with vitamins C and/or E

“…Vitamin E is a powerful antioxidant which extends erythrocyte life and is essential for cell respiration (Hung et al, 1981). Vitamin E deficiency induces erythrocyte fragility, causing their degeneration in many species such as Channel catfish (Wilson et al, 1984;Wise et al, 1993), Atlantic salmon (Hamre et al, 1997), rainbow trout (Furones et al, 1992), and pacu (Belo et al, 2005). Although erythrocyte fragility was not measured, fish fed a vitamin E-deficient diet showed lysed erythrocytes in blood smears.…”