Effects of dietary lipid level and n-3/n-6 fatty acid ratio on growth, fatty acid composition and lipid peroxidation in Russian sturgeon Acipenser gueldenstaedtii

The growth performance, fatty acid composition, hepatic lipid content, hepatic somatic index and lipid peroxidation in Russian sturgeon were investigated using diets containing three lipid levels 50 g kg⁻¹ (L5), 150 g kg⁻¹ (L15) and 250 g kg⁻¹ (L25) and three n-3/n-6 fatty acid ratios (1 : 3, 1 : 1 and 3 : 1) for 8 weeks. Weight gain significantly increased with the increase in dietary lipid levels at n-3/n-6 fatty acid ratios of 1 : 3 and 1 : 1, but not at the 3 : 1 ratio. Correspondingly, fish survival gradually decreased with the increase in dietary lipid at the 3 : 1 n-3/n-6 fatty acid ratio. The dietary lipid level significantly affected the composition of whole-body fatty acid. The retention of highly unsaturated fatty acid dramatically decreased at the level of 250 g kg⁻¹ dietary lipid. The liver malondialdehyde increased with the increase in dietary lipid levels and the n-3/n-6 fatty acid ratios. The contents of lipid and triglyceride in the liver and the hepatic somatic index also increased with the increase in dietary lipid. The diet combination of L25 + 3 : 1 showed the highest aspartate transaminase and alanine transaminase, indicatives of hepatic injury. This study indicates that the L25 + 1 : 3 diet can improve fish growth performance, whereas the L25 + 3 : 1 diet may lead to poor growth performance due to high lipid peroxidation.