Abstract:A feeding trial was carried out to evaluate the effects of dietary fatty acids on growth and proximate composition of juvenile sea cucumber Apostichopus japonicus. Juvenile sea cucumber weighing 1.45g in body weight was stocked into 42 plastic tanks of each 45 cm×31 cm×30 cm for 80 days and fed the commercial 12.70% crude protein and 5.48% crude fat diets containing various proportions of olive oil, linoleic acid (LA), linolenic acid (LNA), docosahexaenic acid (DHA), and eicosapentaenic acid (EPA) with a ratio of LA to LNA=20∶0 （S1）；20∶1（S2）；1∶2（S3）and 2∶1（S4）and with LA∶LNA∶DHA∶EPA=6∶1∶5∶0（S5）；10∶1∶30∶5（S6）and 10∶5∶6∶1（S7）at water temperature of 13.0~23.0 ℃. The sea cucumber fed the diets containing supplement of only olive oil (S1), both olive oil and LNA (S2) and LA and LNA (S3) was found to have the minimal special growth rate (SGR), significantly lower than the animals fed other diets(P < 0.05). There were significantly lower visceral-somatic ratio, and higher intestinal amylase and protease activities, and higher apparent digestibility in the juveniles fed the diet with a ratio of LA∶LNA∶DHA∶EPA= 10∶5∶6∶1（S7）(P < 0.05). Much higher total levels (85.79%) of protein, fat and ash were observed in the juveniles fed the experimental diets than in the initial juveniles(7970%), descendantly ranged as S2（90.57%）> S1（87.97%）> S3（85.78%）> S4（85.29%） > S7（84.19%） > S5（83.79%）> S6（82.97%）.While there was degrowth in LA+LNA levels in the juveniles fed the experimental diets, there was increase in EPA level, varying from 4.36%to 6.83% in the juveniles fed the experimental diets without supplementation of EPA, indicating that dietary 18-C fatty acids were to some extent converted into EPA in the juveniles. The catalase activity was significantly higher in groups S4, S5, S6 and S7 than that in other groups in the juveniles (P < 0.05). High catalase activity appeared in the sea cucumber juveniles when they grew fast, and superoxide dismutase had no apparent variations under different conditions.
