Effects of dietary lipid and phospholipid levels on growth performance, lipid metabolism, and antioxidant capacity of largemouth bass (Micropterus salmoides) larvae.

Abstract

A 42-day feeding trial was conducted to determine the effects of different lipid and phospholipid (PL) levels on growth performance, fatty acid composition, fat deposition, antioxidant capacity, and liver health of largemouth bass (Micropterus salmoides) larvae. Six diets were designed: 6% lipids and 0% PLs (L6/PL0), 3% lipids and 3% PLs (L6/PL50), 0% lipids and 6% PLs (L6/PL100), 12% lipids and 0% PLs (L12/PL0), 6% lipids and 6% PLs (L12/PL50), and 0% lipids and 12% PLs (L12/PL100). These correspond to gradient designs for PLs replacing 0%, 50%, and 100% lipids at the 6% and 12% lipids levels. Results showed that dietary PL supplementation significantly enhanced body weight gain (BWG) and specific growth rate (SGR), with the highest BWG in L12/PL100. PL supplementation reduced both the hepatosomatic index (HSI) and viscerosomatic index (VSI), with the L6/PL100 having the lowest levels. The PL supplementation efficiently reduced liver fat deposition and neutral lipid/polar lipid ratio. The n-3 polyunsaturated fatty acid content in the polar lipid fraction was significantly higher than that in the neutral lipid fraction. Dietary PL supplement significantly increased hepatopancreatic catalase and glutathione activities and decreased malondialdehyde content in the hepatopancreas. PL supplementation significantly reduced liver triglyceride and total cholesterol levels, with the lowest levels observed in the L6/PL100 and L12/PL100 groups. These findings demonstrate that graded PL replacement (up to 100%) at the 6% lipid level optimized growth, reduced fat deposition, increased antioxidant capacity, and avoided the metabolic burden induced by high fat (12% lipids), enhancing LB larval health.