Dietary calcium requirement of fingerling Indian major carp, Labeo rohita (Hamilton) based on growth performance, tissue mineralization, whole body, and serum biochemical composition

Abstract

The dietary calcium requirement of fingerling Labeo rohita (6.0 ± 0.11 cm; 1.94 ± 0.07 g) was examined using seven iso-nitrogenous and iso-caloric purified diets (350 g kg−1 crude protein; 16.72 kJ g−1 gross energy) with incremental levels of calcium (2.14, 3.12, 4.23, 5.11, 6.14, 8.23, and 11.24 g kg−1) that were hand-fed to triplicate groups of fish (20 fish per tank) to apparent satiation for 8 weeks. At the end of the feeding trial, ten fish from each replicate tank (n = 10 × 3) were sampled to obtain serum, scales, and vertebrae. The remaining fish in each tank were sampled to determine proximate chemical body composition. Live weight gain (LWG; 637.6%), protein gain (PG; 2.19 g fish−1), protein retention efficiency (29.89%), and feed conversion ratio (1.69) improved with increased dietary calcium up to 5.11 g kg−1 and then stabilized. Dietary calcium up to 5.11 g kg−1 significantly increased calcium and phosphorus concentrations of whole body, vertebrae, and scales. Fish fed a diet with calcium higher than 5.11 g kg−1 had a significant decrease (P < 0.05) in magnesium and zinc, while potassium was unaffected. Serum alkaline phosphatase activity increased (P < 0.05) with increased dietary calcium up to 5.11 g kg−1, but serum calcium and phosphorus concentrations remained unchanged. Based on broken-line regression analysis of LWG, PG, whole body, vertebrae, and scale calcium content against dietary calcium concentration, dietary calcium in the range of 5.16–5.48 g kg−1 is recommended for fingerling L. rohita.