Leonardite humic acid enhances growth, lipid utilization and antioxidant status in juvenile Penaeus vannamei

A feeding trial of 60-days was conducted to assess the effect of leonardite humic acid (LHA) supplemented varying protein-lipid diets on growth, lipid utilization, and antioxidant status of white-leg shrimp, Penaeus vannamei juveniles reared in inland saline water (ISW). Three hetero-lipidic (50, 70, 90 g/kg lipid), hetero-nitrogenous (360, 330, 300 g/kg CP), and hetero-energetic (374-398 Kcal DE/100 g) diets with three levels of LHA (0, 9 and 12 g/kg) were formulated for nine diets viz. P 36 L 5 LHA 0 (360 g/kg CP, 50 g/kg lipid + 0 g/kg LHA), P 36 L 5 LHA 0.9 (P 36 L 5 LHA 0 + 9 g/kg LHA), P 36 L 5 LHA 1.2 (P 36 L 5 LHA 0 + 12 g/kg LHA), P 33 L 7 LHA 0 (330 g/kg CP, 70 g/kg lipid + 0 g/kg LHA), P 33 L 7 LHA 0.9 (P 33 L 7 LHA 0 + 9 g/kg LHA), P 33 L 7 LHA 1.2 (P 33 L 7 LHA 0 + 12 g/kg LHA), P 30 L 9 LHA 0 (300 g/kg crude protein, 90 g/kg lipid + 0 g/kg LHA), P 30 L 9 LHA 0.9 (P 30 L 9 LHA 0 + 9 g/kg LHA), P 30 L 9 LHA 1.2 (P 30 L 9 LHA 0 + 12 g/kg LHA). Six hundred seventy five juveniles (5.02 ± 0.01 g) were randomly distributed in triplicates following 3 × 3 factorial design. P 33 L 7 LHA 1.2 group exhibited highest WG, SGR, PER, LER, and whole-body protein content, along with lowest FCR, whole-body lipid content, and HPSI. Hepatopancreatic amylase and lipase activities increased significantly with rising dietary lipid levels, whereas protease activity showed a decreasing trend. Hepatopancreatic amylase and lipase activities increased with increasing dietary lipid levels, whereas protease activity was highest in shrimps of P 33 L 7 group and lowest in P 30 L 9 group. Supplementation with LHA enhanced the activity of all digestive enzymes, with the highest activity observed in the group fed 12 g/kg LHA. Lipid metabolic enzyme G 6 PDH and CPT-1 activities were found maximum in P 33 L 7 LHA 1.2 group and lowest in P 36 L 5 LHA 0 group. Hepatopancreatic and branchial SOD and CAT showed a decreasing and increasing trend, respectively, with increasing dietary lipid levels, whereas LHA supplementation showed reduced activities, with lowest in P 33 L 7 LHA 1.2 group. Shrimps fed 12 g/kg LHA showed the lowest levels of MDA, glucose, cholesterol and triglyceride that other groups. Therefore, among the diets tested, 330 g/kg CP, 70 g/kg lipid and 12 g/kg LHA produced the most favorable growth and antioxidant responses of P. vannamei juveniles reared in ISW of 10 ppt.