Effect of supplemental dietary zinc on the growth, body composition and anti-oxidant enzymes of coho salmon (Oncorhynchus kisutch) alevins

Abstract

Zinc (Zn) is a trace element in the animal body, which plays a vital regulatory role in nucleic acid, protein synthesis and anti-oxidative enzymes activities. Therefore, this study was designed to elucidate the role of dietary Zn on growth performance, whole body and vertebral Zn concentrations, the total hepatic anti-oxidative enzymes and alkaline phosphatase (AKP) activities in coho salmon (Oncorhynchus kisutch) alevins. Triplicate groups of alevins (initial body weight: 0.38 ± 0.02 g) were fed dietary treatments containing 13.4, 28.6, 38.5, 44.3, 56.6 and 65.7 mg/kg Zn level, respectively for 12 weeks. Fish were held in 18 tanks (80cm × 60cm × 60 cm, water volume 240-L, 100 fish/tank). At the ending of experiment, the sampling procedure was implemented after 24 h of fasting. The results showed that dietary Zn treatment higher than 44.3 mg/kg significantly increased the specific growth rate (SGR) (P < .05). Zn concentrations in whole-body and vertebrae were increased as dietary Zn concentrations increased from 38.5–65.7 mg/kg (P < 0.01), compared to dietary Zn contents 13.4 and 28.6 mg/kg. The hepatic superoxide dismutase (T-SOD), catalase (CAT) and AKP enzymes activities were increased, however, malondialdehyde (MDA) enzyme activity was decreased as dietary Zn concentrations increased from 28.6–65.7 mg/kg (P < .01). There were no significant differences (P > .05) in whole-body moisture, crude protein, crude lipid and ash in all the dietary treatments. These results indicated proper dietary Zn supplementation improved SGR and anti-oxidative enzyme activities. Based on the results analysis of SGR, Zn contents in whole-body and vertebrate and liver T-SOD and AKP activities, the optimal dietary Zn levels for coho salmon alevins were estimated to be 54.0, 59.3, 54.5, 59.8 and 53.8 mg/kg, respectively.