Effect Of Partial Replacement Of Fish Oil With Vegetable Oil On Growth, Body Lipids And Fatty Acid Of Larvae Larmichthys Crocea

Lipid and fatty acids from feed are important structure materials and energy source for marine fish. Rencent years, the needs of marine fish oil for aquaculture was much greater than the supply of marine fish oil, the cost of aquatic feed went up, it was eager to find a cost-effective lipid source to replace fish oil. The vegetable oil is considered to be a good substitute for fish oil, which had a advantage of high yield, low price, and renewable. In order to investigate the effect of partial replacement of fish oil with vegetable oil on growth, body lipids and fatty acid of larvae Larmichthys crocea, Six isonitrogenous and isoenergetic experimental diets were formulated. The control feed(Group A) was formulated with 6% fish oil, whereas the other 5 experimental diets were formulated by replacing the fish oil with 16.67% rapeseed oil(Group B), 33.33% rapeseed oil(Group C), 50% rapeseed oil(Group D), 66.67% rapeseed oil(Group E), and 66.67% blended vegetable oil(Group F,palm oil: perilla oil: rapeseed oil = 3.6 : 2.5 : 1), respectively. A 50-day feeding trial was conducted(initial weight 0.65±0.11g), and we sampled then analyzed the lipid and fatty acids of larvae Larmichthys crocea at different feeding time, in order to verify the effect pattern of replacement on the growth and fatty acid composition of Larvae Larmichthys crocea, and provide a reference for low-cost formula feed of the larvae Larmichthys crocea. The results showed that:1.The final weight, weight gain, specific growth rate, condition factor of these replacements(Group B、C、D、E and F) did not significantly influence compared with Group A(control group)(P>0.05). t The survival rate of Group C(33.33%), D(50.00%) and E(66.67%) were lower than Group A(control group). The hepatosmatic index in Group B(16.67%), C(33.33%) and D(50.00%) was significantly higher than that in Group A(control group)(P<0.05), while Group E(66.67%) and F(blended vegetable oil group) has no significantly differences in hepatosmatic index with Group A(control group)(P>0.05). There was no significant difference in feed coefficient among the six experimental groups(P>0.05). Partial replacement of fish oil with vegetable oil has significantly influenced on the content of muscle protein. Group A(control group) displayed the lowest protein content in muscle(58.9±0.41%). There was no significant difference in ash among the six experimental groups(P>0.05). There was no significant influence on total lipid contant in muscle or liver among six experiment groups. Fatty acid composition among the treatments was significantly changed. With the increasing replacement of fish oil by rapeseed oil, the contant of 18:3n3 in muscle and the contant of 18:1, 18:2n6, 18:3n3 in liver were significantly increased(P<0.05), whereas the contant of EPA and DHA were significantly decreased(P < 0.05). Compared to those in Group E, the contant of EPA, DHA in muscle and the contant of 18:3n3 in liver in Group F(blended vegetable oil group) were significantly increased, whereas the contant of EPA and DHA in liver were significantly decreased(P<0.05).2. Fish condition factor was not affected by replacement and feeding time(P>0.05). The hepatosmatic index of Group E(66.67%) in day 20, 40 was significantly increased(P<0.05). There was no significant differences among the other groups in any time. At the meantime, total lipid of muscle and liver has no significant difference at any feeding time(P>0.05). However, partial replacement of fish oil with vegetable oil has significantly changed the fatty acid profiles in muscle and liver. With the increasing level replacing by rapeseed oil, the contant of 18:1, 18:2n6, 18:3n3 in muscle were significantly increased. Compared with that in A group(control group), 18:1 of Group B(16.67%) increased significantly in day 30, and in day 10 for other groups; the contant of 18:2n6 increased significantly at day 10 in Group D(50.00%) and E(66.67%), at day 20 in Group C(33.33%) and at day 40 in Group B(16.67%). The contant of 18:3n3 increased significantly at day 10 in Group D(50.00%) and E(66.67%), at day 20 in Group C(33.33%) and at day 30 in Group B(16.67%). The contant of 18:1, 18:2n6 and 18:3n3 in Group F(blended vegetable oil group) significantly increased at day 20, day 20 and day 10, respectively. The composition of 18:1, 18:2n6 and 18:3n3 increased significantly at day 10 in liver. The composition of EPA and DHA were gradually decreased as the replaced level increased. The results suggested that replaced fish oil with vegetable oil did not influence total lipid of the fish at any time, however, it significantly changed the fatty acid profiles of the fish. The fatty acid profiles of muscle and liver were not only influenced by the dietary fatty acid, but also the feeding time.