Dietary manganese requirement of fingerling Indian major carp, Labeo rohita (Hamilton) estimated by growth, tissue manganese concentration and hepatic manganese-superoxide dismutase activity

Abstract

Dietary manganese requirement of Labeo rohita fingerlings (6.4 ± 0.12 cm; 2.3 ± 0.07 g) was estimated by feeding seven isonitrogenous and isoenergetic (350 g kg−1 crude protein; 16.7 kJ g−1 gross energy) test diets with different manganese concentrations (1.6, 2.6, 5.1, 11.1, 20.3, 40.2 and 80.1 mg kg−1 diet). The test diets were hand-fed to triplicate groups of fish at 08:00, 12:00 and 16:00 h to apparent satiation for 8-week. Live weight gain (LWG), protein efficiency ratio, specific growth rate, feed conversion ratio, protein gain, manganese concentration in the scales, vertebrae and whole body, and hepatic manganese-superoxide dismutase (Mn-SOD), total superoxide dismutase, catalase, glutathione peroxidise and lipase activities improved significantly (P < .05) in fish fed diets containing increasing manganese concentrations up to 11.1 mg kg−1 and then stabilized. Maximum apparent manganese retention (P < .05) was recorded in groups fed with 1.6 and 2.6 mg kg−1 dietary manganese levels followed by a significant decrease in fish fed higher levels of dietary manganese. Dietary manganese supplementation exerted no significant effects (P > .05) on the body moisture and ash contents, but showed a significant influence (P < .05) on the protein and fat contents, viscerosomatic index, hepatosomatic index, and condition factor. Increase in dietary manganese levels significantly affected (P < .05) whole body, vertebrae, scales and liver mineralization, except copper concentration. Hepatic malondialdehyde (MDA) concentration and lactate dehydrogenase (LDH) activity significantly decreased with increment in manganese levels up to 11.1 mg kg−1 diet. Broken-line regression analysis of LWG, scales, whole body and vertebrae manganese concentration, and hepatic Mn-SOD activity against dietary manganese concentrations, indicated the manganese requirement of L. rohita fingerlings in the range of 9.4–10.9 mg kg−1 of diet.