Effect of L-carnitine supplementation on growth performance, feed utilization, body composition, and antioxidant capacity of large yellow croaker, Larimichthys crocea, fed at two dietary lipid levels

Exploring the influence of dietary L-carnitine (LC) supplementation in fish diets with varying lipid levels is essential for comprehending its effects. The present study assessed the effect of dietary LC supplementation on growth performance, feed utilization, body composition, and antioxidant capacity of large yellow croaker (Larimichthys crocea) at two dietary lipid levels. Two diets were formulated with 100 g kg⁻¹ and 140 g kg⁻¹ lipid levels as control diets, which were each supplemented with four LC levels at 0, 0.2, 0.3, and 0.4 g kg⁻¹ to make the experimental diets. These diets were fed to fish weighing 10.80 ± 0.40 g for eight weeks. The results showed that dietary lipid and LC levels, and their interaction affected final body weight and weight gain of fish. The fish fed at 140 g kg⁻¹ dietary lipid level supplemented with 0.2 (HC2) and 0.3 (HC3) g kg⁻¹ LC increased weight gain by 5% and 23%, respectively, compared to those fed on the control diet (HC0). Moreover, the fish fed at 100 g kg⁻¹ dietary lipid level supplemented with 0.2 (LC2), 0.3 (LC3), and 0.4 (LC4) g kg⁻¹ LC increased weight gain by 12.6%, 5.8%, and 8.3% compared to those fed the control diet (LC0). Independently, dietary lipid and LC levels affected serum superoxide dismutase and liver catalase activities. Dietary lipid level affected body lipid and energy contents, serum malondialdehyde content, and liver glutathione peroxidase activity. The optimum dietary LC required for maximum weight gain was 0.31 g kg⁻¹ for fish fed the diet containing 140 g kg⁻¹ lipid level. The present study reveals that the effect of dietary LC varies at different lipid levels. We recommend adding 0.31 g kg⁻¹ LC during the formulation of diets containing 140 g kg⁻¹ lipid to improve growth performance of large yellow croaker during commercial farming.