Effects of Dietary Arachidonic Acid (20:4n-6) Levels on Growth Performance and Fatty Acid Composition of Juvenile Eel, Anguilla japonica

This study was conducted to evaluate the effects of dietary arachidonic acid (AA, 20:4n-6) levels on growth performance and body composition in juvenile eel, Anguilla japonica. Six semi-purified experimental diets were formulated to be iso-nitrogenous and iso-caloric containing 55.0% crude protein and 15% crude lipid (18.3 kJ of available energy g(-1)). Six different levels of AA were added to the basal diet with 0, 0.2, 0.4, 0.6, 0.8 or 1.2% on a dry matter (DM) basis, respectively (AA(0.07), AA(0.22), AA(0.43), AA(0.57), AA(0.78) or AA(1.23)). After a conditioning period, fish initially averaging 27 +/- 0.5 g (mean +/- SD) were randomly distributed into each aquarium as triplicate groups of 20 fish each. One of six experimental diets was fed on a DM basis to fish in three randomly selected aquaria at a rate of 2-3% of total body weight twice a day. At the end of the 12-week feeding trial, weight gain (WG) and feed efficiency (FE) of fish fed AA(0.78) and AA(1.23) diets were significantly higher than of fish fed AA(0.07), AA(0.22) and AA(0.43) diets (p<0.05). Specific growth rate (SGR) of fish fed the AA(0.78) diet was significantly higher than of fish fed AA(0.07), AA(0.22) and AA(0.43) diets (p<0.05). However, there were no significant differences in WG, SGR and FE among fish fed AA(0.57), AA(0.78) and AA(1.23) diets (p>0.05). Whole body AA deposition of fish fed the AA(1.23) diet was significantly higher than for the other diets (p<0.05). Broken-line model analysis on the basis of WG and SGR indicated that the dietary AA requirement could be greater than 0.69% but less than 0.71% of the diet in juvenile eel. The growth-promoting activity of AA observed in the present study provides strong support for the contention that dietary AA is essential for juvenile eel.