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

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 x 60cm x 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.

Automated summary

This study found that proper dietary zinc supplementation can improve growth performance and antioxidative enzyme activities in coho salmon alevins, but excess zinc in the diet may have negative effects.