Glycerol monolaurate improves growth, lipid utilization and antioxidative status of white-leg shrimp, Penaeus vannamei fed with varying protein-lipid diets reared in inland saline water

Abstract

Higher lipid at suboptimum dietary protein level can be a suitable approach to formulate cost-effective feed for cultured fish. However, excess lipid may cause metabolic burden to animals resulted in growth retardation with lipid deposition. Therefore, a feeding trial of 60 days was conducted to assess the effect of glycerol monolaurate (GML) supplemented in varying protein and lipid diets on growth, lipid utilization, antioxidant status and biochemical indices of white-leg shrimp, Penaeus vannamei juveniles reared in inland saline water (ISW). Accordingly, three hetero-lipidic (5–9% lipid), hetero-nitrogenous (30–36% CP), and hetero-energetic (379–400 Kcal DE/100 g) diets with three levels of GML (0%, 0.07% and 0.1%) were formulated for nine diets viz. P36L5G0 (36% CP, 5% lipid and 0% GML), P36L5G0.07 (36% CP, 5% lipid and 0.07% GML), P36L5G0.1 (36% CP, 5% lipid and 0.1% GML), P33L7G0 (33% CP, 7% lipid and 0% GML), P33L7G0.07 (33% CP, 7% lipid and 0.07% GML), P33L7G0.1 (33% CP, 7% lipid and 0.1% GML), P30L9G0 (30% CP, 9% lipid and 0% GML), P30L9G0.07 (30% CP, 9% lipid and 0.07% GML) and P30L9G0.1 (30% CP, 9% lipid and 0.1% GML). Five hundred and forty P. vannamei juveniles (4.02 ± 0.01 g) were randomly distributed following 3 × 3 factorial design. Highest (p < 0.05) weight gain. Specific growth rate, protein efficiency ratio, lipid efficiency ratio, whole body protein with lowest feed conversion ratio, whole body lipid, and hepatopancreas–somatic index was recorded in P33L7G0.1 group. Hepatopancreatic amylase and lipase activities increased (p < 0.05) significantly while protease activity decreased in relation to increased levels of dietary lipid. However, supplementing GML resulted in increased (p < 0.05) activity of all digestive enzymes and highest activity was found in 0.1% GML fed group. Lipid metabolic enzyme glucose-6-phosphate dehydrogenase and carnitine palmitoyltransferase-1 activities were found maximum (p < 0.05) in P33L7G0.1 group and lowest in P36L5G0 group. Hepatopancreatic and branchial superoxide dismutase and catalase activities showed a decreased (p < 0.05) and increased trend with dietary lipid levels, while GML reduced the activities and lowest activity recorded in P33L7G0.1 group. Shrimps of 9% lipid group exhibited highest serum malondialdehyde, glucose, cholesterol and triglyceride levels but 0.1% GML significantly showed the lowest levels that other groups. Higher hemocyanin and total protein observed in 33% dietary protein and 0.1% GML fed group. Therefore, 33% protein, 7% lipid with 0.1% GML is optimum for maximum growth performance, lipid utilization, whole body protein, and antioxidative status of white-leg shrimp, P. vannamei juveniles reared in ISW of 10 ppt.