Effects of dietary magnesium supplementation on growth, feed utilization, nucleic acid ratio and antioxidant status of fingerling Heteropneustes fossilis

Abstract

To investigate the effects of dietary magnesium on growth, feed utilization, nucleic acid ratio and antioxidant status of Heteropneustes fossilis and determine the optimum dietary magnesium requirement, basal diet (400 g/kg crude protein and 17.89 MJ/kg gross energy) supplemented with magnesium sulfate at 0, 2.02, 4.05, 6.08, 8.11 and 10.14 g/kg diet, yielding 0, 0.20, 0.40, 0.60, 0.80 and 1.0 g magnesium per kg of the diet were fed to triplicate groups of fishes. Analyzed values of dietary magnesium were found to be 0.06, 0.28, 0.45, 0.68, 0.88 and 1.05 g/kg. Increasing dietary magnesium levels significantly (P < 0.05) enhanced the absolute weight gain (AWG), specific growth rate (SGR), RNA-DNA ratio, protein retention efficiency (PRE) and protein gain (PG) up to 0.68 g/kg. Biometric indices were also found to improve up to 0.68 g/kg magnesium and then remained static. Antioxidant status in terms of superoxide dismutase (SOD), catalase (CAT) and malondialdehyde (MDA) also exhibited significant improvement (P < 0.05) in response to incremental levels of dietary magnesium up to 0.68 g/kg. The whole-body composition also reflected significant changes up to magnesium level of 0.68 g/kg diet. Serum alkaline phosphatase (ALP) activity and magnesium concentration improved with the increasing magnesium level up to 0.88 g/kg diet. Improvement in whole-body and vertebrae mineralization in response to increasing dietary magnesium levels was also noted up to 0.88 g/kg diet. Broken-line regression analysis of SGR, PG, RNA-DNA ratio, serum SOD activity and vertebrae magnesium data against increasing levels of dietary magnesium indicated the optimum requirement of H. fossilis in the range of 0.65−0.79 g/kg diet.