A 65-day trial was conducted to investigate effects of CLA on cytological morphology, activity of antioxidant enzymes, and gene expressions of lipid metabolism in the liver and muscle of grass carp. Seven isonitrogenous (crude protein: 36 g/100 g) and isolipidic (crude lipid: 4.5 g/100 g) diets were formulated: 0 CLA (control), 0.5% (CLA0.5), 1% (CLA1), 1.5 (CLA1.5), 2 (CLA2), 2.5 (CLA2.5), and 3% CLA (CLA3). Three biological replicates of fish were assigned to each diet with the initial body weight at (5.08±0.08) g. Endoplasmic reticulum in t...