Effect of dietary vitamin E on growth, tissue lipid peroxidation, and liver glutathione level of juvenile hybrid tilapia, Oreochromis niloticus×O. aureus, fed oxidized oil
Introduction
Vitamin E is a lipid-soluble vitamin that comprises four tocopherols and four tocotrienols in nature. Among them, α-tocopherol has the highest vitamin E activity (NRC, 1993). Other than its vitamin E activity, α-tocopherol is a potent biological antioxidant that can protect biological membranes and lipid components containing unsaturated fatty acids against attack from oxygen free radicals.
Tilapia is one of the major farmed fish species on the global scale. Studies have shown that the requirement of tilapia for vitamin E may vary due to the difference in dietary lipid source and level Watanabe et al., 1981, Satoh et al., 1987, Schwarz et al., 1988, Roem et al., 1990, Shiau and Shiau, 2001. A recent study has shown that hybrid tilapia require both n-3 and n-6 unsaturated fatty acids for their optimal growth (Chou and Shiau, 1999). The requirement of this fish for dietary highly unsaturated fatty acids (HUFA) also would increase the susceptibility of fish to peroxidative stress. Hybrid tilapia fed diets containing higher level of n-3 HUFA had higher proportion of n-3 HUFA in their muscle and sarcoplasmic reticulum (SR) than fish fed a diet low in these fatty acids (Huang et al., 1998). This also resulted in greater lipid peroxidation in their biological membranes compared to fish fed diets containing less unsaturated fatty acids. However, when dietary vitamin E level increased, lipid peroxidation in post-mortem tilapia muscle and SR was inhibited (Huang et al., 2004).
One other factor that may affect the dietary vitamin E requirement is the oxidative stability of the diets. Baker and Davies (1996) reported that the growth of African catfish was suppressed when lipids in their diets were oxidized. Addition of vitamin E to rancid diets significantly improved growth performance of the fish. For sub-tropical and tropical regions such as Taiwan, the climate is humid and the temperature is high throughout the year especially in summer time. Lipids in fish diets could be oxidized rapidly when storage condition is not satisfactory. Hence, it is important to understand the impact of oxidized lipids on the requirement of vitamin E for locally cultured fish. The purpose of this study was to investigate the dietary vitamin E requirement of hybrid tilapia fed oxidized oil. The effects of dietary vitamin E on liver glutathione (GSH) level and ascorbate-induced lipid peroxidation in both liver and muscle were investigated as well.
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Materials and methods
Juvenile hybrid tilapia (Oreochromis niloticus×O. aureus) obtained from Yi-Hwa Hatchery Farm (Tainan, Taiwan) were transferred to our laboratory and reared in a 500-l fiberglass tank prior to the experiment. The basal diet with no added vitamin E was used to adjust the fish to the laboratory condition 2 weeks before the experiment. After the acclimation, fish were selected and randomly stocked into 18 glass aquaria containing 90 l of water per aquarium (75L×30W×45 cm H) at a density of 20 fish
Results
Growth performance of the fish fed different level of vitamin E is presented in Table 2. Weight gain (WG) of the fish fed diets containing 0 IU vitamin E/kg was significantly lower (P<0.05) than those fed higher vitamin E (>80 IU/kg) diets. Feed conversion ratio (FCR) and protein efficiency ratio (PER) followed similar trends as growth performance. Survival ranged from 95% to 98.3%. No difference in survival among test groups was observed. Based on the WG, the estimated dietary vitamin E
Discussion
Dietary vitamin E requirement of tilapia has been studied with various results. Many factors such as lipid level, source, and other antioxidants or antioxidant enzymes presented in the diet or body system may affect the dietary vitamin E requirement of fish. Satoh et al. (1987) reported that inclusion of 50–100 mg α-tocopherol/kg diet was sufficient for tilapia fed diets containing 5% lipid. However, the study from Roem et al. (1990) suggested that the vitamin E requirement of blue tilapia was
Acknowledgements
The funding of this study was provided by the National Science Council under project number NSC-90-2313-B-415-001. We thank Y.H. Chiou of Yi-Hwa Hatchery Farm for supplying the juvenile hybrid tilapia.
References (26)
- et al.
Optimal dietary lipid level for growth of juvenile hybrid tilapia, Oreochromis niloticus x O. aureus
Aquaculture
(1996) - et al.
A simple method for the isolation and purification of total lipids from animal tissue
J. Biol. Chem.
(1957) - et al.
Effects of dietary vitamin E levels on oxidative stability of trout fillets
Aquaculture
(1990) - et al.
Effect of dietary lipids on fatty acid composition and lipid peroxidation in sarcoplasmic reticulum of hybrid tilapia (Oreochromis niloticus×O. aureus)
Comp. Biochem. Physiol., B
(1998) - et al.
Increased activities of hepatic antioxidant defence enzymes in juvenile gilthead sea bream (Sparus aurata L.) fed dietary oxidized oil: attenuation by dietary vitamin E
Aquaculture
(2002) - et al.
Estimation of nutrient requirements from growth data
J. Nutr.
(1979) - et al.
Vitamin E requirements of blue tilapia, Oreochromis aureus (Steindachner), in relation to dietary lipid level
Aquaculture
(1990) - et al.
Influence of different fats with varying additions of α-tocopherol acetate on growth and body composition of carp (Cyprinus carpio L.)
Aquaculture
(1988) - et al.
Vitamin E sparing effect by dietary vitamin C in juvenile hybrid tilapia, Oreochromis niloticus×O. aureus
Aquaculture
(2002) - et al.
Lipid peroxidation in turbot (Scophthalmus maximus) tissue: effect of dietary vitamin E and dietary n-6 or n-3 polyunsaturated fatty acid
Aquaculture
(1995)