Abstract
This study investigated the effect of dietary Zn levels on growth performance, feed utilization, and hematological parameters of juvenile Siberian sturgeon (Acipenser baerii, Brandt 1869). The five semi-purified diets were formulated by adding 0, 5, 10, 20, and 40 mg Zn kg−1 diet in the form of zinc sulfate (ZnSO4) to provide the actual dietary value of 14.7, 20.8, 27.3, 37.7, and 46.4 Zn kg−1 diet, respectively. The results showed that dietary Zn elevating level significantly improved the growth and feed utilization of the fish (p < 0.05), but not the hepatosomatic index (p > 0.05). Erythrocyte number, hemoglobin concentration, and hematocrit were increased with raising dietary Zn level (p < 0.05), whereas a regular trend was not observed in blood indices, including MCV, MCH, and MCHC. A significant increase was also found in the leucocyte number followed by their differential counts, except for eosinophil percentage. The broken line regression model indicated optimal dietary Zn level for growth maximization of fish was estimated to be 29.15 mg Zn kg−1 diet. In spite of well correlation with dietary Zn level, no break point was observed to estimate the juvenile Siberian sturgeon requirement based on the erythrocyte numbers.
Highlights
Zinc (Zn) is an essential micro-mineral required for various metabolic pathways, including growth, protein synthesis, energy metabolism, and immunity of animals, including fish (Houng-Yung et al 2014; Lin et al 2013)
No mortality and abnormal behavior were observed in dietary treatments of Siberian sturgeon juveniles during the experimental period
The results indicated that dietary Zn level affected the growth performance of fish as final weight, and specific growth rate (SGR) and hepatosomatic index (HSI) values increased following the Zn level enhancement in experimental diets
Summary
Zinc (Zn) is an essential micro-mineral required for various metabolic pathways, including growth, protein synthesis, energy metabolism, and immunity of animals, including fish (Houng-Yung et al 2014; Lin et al 2013). Fish can uptake the Zn directly from the surrounding water via the gills, ambient waterborne Zn concentration in most freshwaters is known to be suboptimal to meet their metabolic requirements and a dietary supplementation is necessary to compensate for low dietborne Zn concentration (Gatlin and Phillips 1989; Fountoulaki et al 2010; Luo et al 2011). Dietary Zn level should be in an optimal range which can decrease the feed cost and prevent mineral leaching in aquatic environments (Buentello et al 2009; Huang et al 2015)
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