MUSCLE AND HEPATIC FATTY-ACID PROFILES AND ALPHA-TOCOPHEROL STATUS INAFRICAN CATFISH (CLARIAS-GARIEPINUS) GIVEN DIETS VARYING IN OXIDATIVESTATE AND VITAMIN-E INCLUSION LEVEL

On termination of a 56-day feeding trial, the effect of dietary oxidiz ed oil and all-rac-alpha-tocopheryl acetate on fatty acid and alpha-to copherol status of juvenile African catfish (Clarias gariepinus) muscl e and liver was investigated Clarias of mean initial weight 15.8 (s.e. 0.29) g were given food at proportionately 0.03 body weight per day o n diets of two oxidative states (fresh or oxidized) at two levels of s upplemental alpha-tocopheryl acetate (20 or 100 mg/kg dry matter). As well as having a significant detrimental effect on final body weight ( P < 0.001), oxidation of the dietary lipid source was responsible for decreasing muscle but not hepatic polyunsaturated fatty acids (PUFAs). Liver tissue ions suspected of actively synthesizing longer chain PUF As in response to consumption of oxidized oils, as indicated by decrea ses in the proportions of linoleate (18:2 n-6) and linolenate (18:3 n- 3) and the increased abundance of eicosatetraenoic acid (20:4 n-6, ara chidonate) and docosahexaenoic acid (22:6 n-3, DHA). This phenomenon h as not been described in fish nutrition and therefore possible mechani sms are discussed. Additionally, oxidized oils in catfish diets caused significant depletion of alpha-tocopherol from both muscle and liver (P < 0.05). Modulation of the effects of oxidized lipids was achieved at the higher dietary tocopherol concentration. Appearance of an unkno wn aliphatic compound (equivalent chain length (ECL) = 13.1), believed to be a product of lipid peroxidation, demonstrated that catfish give n rancid/low-tocopherol diets had been subjected to heightened oxidati ve nutritional stress. Values obtained for this peak were significantl y correlated with dietary regime (P < 0.01). Once move, dietary alpha- tocopheryl acetate moderated this effect. It was concluded that elevat ed inclusion of all-rac-alpha-tocopheryl acetate into diets for Africa n catfish could abrogate the effects of oxidized dietary lipids on mus cle and liver fatty acids and alpha-tocopherol.