Effects of dietary conjugated linoleic acid on growth, antioxidant capacity and lipid metabolism of Macrobrachium nipponense

Dietary conjugated linoleic acids (CLA) have been shown to alter growth rates, improve antioxidant capacity and modulate lipid metabolism in higher animals including some species of fish, but have not been evaluated in economic crustaceans. An 8-weeks feeding trial was conducted to evaluate the effects of dietary CLA on growth, antioxidant capacity and lipid metabolism of oriental river prawn, Macrobrachium nipponense. Five semi-purified diets were supplemented with different levels of CLA (CLA1, 0%; CLA2, 1.5%; CLA3, 3%; CLA4, 4.5%; CLA5, 6%). Each diet was fed to juvenile prawns (mean weight, 0.102±0.0024 g) twice daily to apparent satiation in five replicates. The survival rate was influenced by dietary CLA content, and the survival rate of CLA5 significantly decreased compared with that of CLA1 (P < 0.05). No significant difference was observed on weight gain among all groups. Activity of superoxide dismutase (SOD), total antioxidant activity competence (T-AOC) and malondialdehyde (MDA) level in hepatopancreas decreased first, and then increased as CLA level was increased. The SOD activity in prawns fed CLA1 was significantly higher than that of other treatments (P < 0.05). The hepatopancreas MDA content was significantly increased when the CLA inclusion was above 4.5% (P < 0.05). The total cholesterol concentration (TC) and total triacylglycerol concentration (TG) in plasma were also significantly affected by dietary CLA levels. Gradually decreased TG and TC were observed with the increase of CLA level (P < 0.05). The mRNA expressions of carnitine palmityltransferase-1 (CPT1), Acetyl CoA carboxylase (ACC) and scavenger receptor class B type Ⅰ (SR-BI) in hepatopancreas were highly sensitive to dietary CLA. The 4.5% CLA level induced the highest CPT1 and SR-BI mRNA expression levels. Similarly, ACC mRNA expression was also the highest in prawns fed the CLA4 diet, which was significantly higher than that of other groups (P < 0.05). These findings demonstrated that (1) CLA inclusion could improve the antioxidant capacity and modulate lipid metabolism; (2) Dietary CLA had little potential for improving growth responses of M. nipponense, and a high proportion (6%) of CLA would reduce the survival rate of prawns.