Dietary folic acid improved growth performance, immuno-physiological response and antioxidant status of fingerling Siberian sturgeon, Acipenser baerii (Brandt 1896)

Abstract

To investigate the effect of dietary folic acid (FA) on growth performance, proximate composition, blood parameters, antioxidant status, and immune response of Siberian sturgeon, Acipenser baerii, six isonitrogenous and isolipidic experimental diets were formulated to contain graded levels of FA (0.60, 1.63, 2.71, 3.59, 4.82, and 5.68 mg kg−1). Each diet was fed to triplicate groups of fish (4.36 ± 0.18 g) in a flow through water system for 8 weeks. Weight gain ratio (WGR) and specific growth rate (SGR) were thrived with increasing FA level up to 2.71 mg kg−1 and decreased gradually thereafter (P < 0.05). The whole-body crude protein content was also highest in fish fed with 2.71 mg FA kg−1 diet followed by those fed 3.59 and 1.63 mg FA kg−1 diet. The muscle and liver FA concentrations were enhanced with increasing dietary FA supplementation with the values significantly higher in fish fed diets supplemented by equal to or more than 3.59 and 4.82 mg FA kg−1, respectively. Red blood cells (RBCs), white blood cells (WBCs), hemoglobin (Hb), hematocrit (Hct), and lymphocyte count showed significant positive correlation with dietary FA level, whereas the neutrophil count was significantly declined by enhancing dietary FA supplementation (P < 0.05). Serum superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) activities were also intensified by increasing dietary FA concentration. Fish fed diets supplemented with more than 1.63 and 2.71 mg FA kg−1 had significantly higher lysozyme activity and immunoglobulin M (IgM) compared to those fed the basal diet. The dietary FA requirement of fingerling Siberian sturgeon was estimated by subjecting the SGR, crude protein content, liver FA content, and WBC count against varying levels of dietary FA which revealed the FA requirement in the range of 1.82–4.41 mg kg−1.