EFFECT OF DHA ON THE GROWTH PERFORMANCE AND LIPID METABOLISM IN TWO DIETARY LIPID LEVELS OF COMMON CARP, CYPRINUS CARPIO L.

In order to evaluate the effect of DHA on the growth and lipid metabolism of common carp (Cyprinus carpio L.), using casein, dextrin, cellulose, soybean oil and fish compound premix as the raw feed two diets with lipid level of 6% and 12% were prepared for Cyprinus carpio L. 3% soybean oil in the two diets was replaced by 50% DHA to produce four diets, which included 6L group, 6L-DHA group, 12L group and 12L-DHA group. A total of 360 common carps (14.81±0.13 g) were randomly divided into four groups (triplicate per group), and fed with four diets, respectively, for 74 days. After then, growth performance, biological parameters, body composition, serum biochemical indicators and tissue morphological were determined. The results showed that compared with 6L group, the feed efficiency, absolute growth rate and relative growth rate decreased significantly in 6L-DHA group (P<0.05). The absolute growth rate was significantly lower in 12L-DHA group than that of 12L group (P<0.05). The intraperiotenal fat index and adipocyte area of intraperiotenal fat tissue were significantly lower in 6L-DHA group than that in 6L group (P<0.05). The crude lipid content in the muscle decreased significantly in DHA diet (P<0.05). However, the content of serum total cholesterol increased significantly in DHA diet. Results showed that the growth and health status of common carp were compromised by adding DHA in lipid diets, which was probably caused by the high level of DHA in diet and it would be avoided by increasing dietary lipid level.