Dietary manganese requirement of Cirrhinus mrigala juveniles

This experiment determined the Mn requirement of Cirrhinus mrigala and evaluated its effects on growth indices and health status. Six experimental diets were prepared containing 0, 5, 10, 15, 20 and 25 mg/kg Mn from MnSO₄·H₂O and analyzed Mn contents were 1.48, 6.37, 11.24, 16.35, 20.8 and 26.15 mg/kg, respectively. A total of 270 C. mrigala juveniles (average initial weight 12.784 ± 0.613 g) were acclimatized and distributed to eighteen aquaria (70 L capacity and 15 fish/aquarium). Each experimental diet was fed in triplicate up to satiation for 60 days. After completion of trial, growth performance and feed intake increased with increasing Mn concentrations in diets up to 26.15 mg/kg. However, feed conversion ratio (FCR) decreased with increasing Mn concentration up to 16.35 mg/kg. Furthermore, whole-body proximate composition improved with increasing Mn concentrations up to 16.35 mg/kg. Mn content in vertebrae, whole body, muscles, kidney and scales significantly increased with increments in Mn concentrations in the diet, however, Mn absorption reached at saturation at 16.35 mg/kg. Hepatic alkaline phosphatase and antioxidant enzymes activities increased significantly with increasing Mn concentrations up to16.35 mg/kg in the diet, while opposite trend was observed in thiobarbituric acid reactive substances (TBARS) content. Based on weight gain%, FCR, Mn content in vertebrae and TBARS content, dietary Mn requirements of the C. mrigala juveniles were assessed to be 13.18, 16.35, 17.22 and 16.45 mg/kg, respectively. In conclusion, C. mrigala require 13.18-17.22 mg/kg Mn in diet for optimum growth performance and health status.