Effects of dietary Zn on growth performance, antioxidant responses, and sperm motility of adult blunt snout bream, Megalobrama amblycephala

A growth experiment was conducted to estimate the effects of dietary Zn on growth, antioxidant responses, and sperm motility of adult blunt snout bream, Megalobrama amblycephala. Six experimental diets were formulated, each containing graded levels of Zn (0, 20, 40, 80, 160, and 320mg/kg, respectively) supplied as ZnSO4·7H2O, providing the actual dietary Zn values of 7.8, 32.7, 50.3, 87.2, 165.4, and 328.5mg/kg diet, respectively. Each diet was assigned to three replicate groups of 15 fish (mean initial body weight: 128.6±0.7g) for 12weeks. Results showed that weight gain (WG) and whole body Zn content increased linearly with increasing dietary Zn levels, then remained nearly unchanged when Zn levels reached the 50.3 and 87.2mg/kg diets, respectively. Fish fed with the control diet had a significantly higher feed conversion rate than those fed with Zn supplemented diets (P0.05), but had a significant effect on moisture, lipid and ash content (P