Evaluation of optimum dietary vitamin E requirements using DL‐α‐tocopheryl acetate in the juvenile eel, Anguilla japonica

Summary The study aimed at evaluating the optimum dietary vitamin E requirements using DL-α-tocopheryl acetate in the juvenile eel, Anguilla japonica, as assessed by fish growth performance and fish body composition. Five semi-purified experimental diets were formulated to contain 0 (TA1), 15 (TA17), 30 (TA32), 60 (TA62) and 120 (TA119 mg TA kg−1 diet on a dry matter (DM) basis in the form of DL-α-tocopheryl acetate (TA). After a 4-week conditioning period, fish (15 ± 0.3 g) were randomly distributed into aquaria in groups of 20 at 25 ± 1.0°C (mean ± SD). One of the five diets was fed on a DM basis to fish in three randomly selected aquaria twice daily to satiation (approximately 3% of wet body weight per day at the beginning and 2% of wet body weight per day at the end of the feeding trial) for 12 weeks. At the end of the 12-week feeding trial, weight gain (WG), specific growth rate (SGR), feed efficiency (FE) and protein efficiency ratio (PER) were determined; these were significantly lower in control fish than in fish fed supplemented diets (P   0.05). There were also no significant differences in SGR among fish fed TA32, TA62 or TA119 (P > 0.05). A broken-line regression analysis on the basis of WG, SGR, FE and PER showed that dietary vitamin E requirements of juvenile eels were 21.2, 21.6, 21.2 and 21.5 (mg kg−1 diet), respectively. These results indicate that the dietary vitamin E requirement could be <21.2 mg kg−1 but <21.6 mg kg−1 diet in juvenile eel, A. japonica, when DL-α-tocopheryl acetate is used as the dietary vitamin E source.