Effects of zinc added to diet on the growth parameters of carp juvenile (Cyprinus carpio)

The common carp (Cyprinus carpio) is a protein source with important economic value and high nutritional quality. Therefore, its cultivation in farms is widely practiced in the world. Carp food constitutes the highest amount of the all expenditure of the fish ranch. Consequently, proper mineral supplementation in the early growth phases and at an early month is Vital to support carp growth. The current research investigated the effect of different level of zinc added to diet on the growth parameters (weight gain WG; proportional growth in weight, PG; specific growth rate, SGR; feed conversion rate, FCR; condition factor, CF), and antioxidant parameters (superoxide dismutase, SOD and catalase, CAT) of the common carp juveniles. For this aim, four iso-nitrogenous (35% crude protein) practical diets were produced with graded levels of dietary zinc sulphate added to the basal diet to provide the following dietary treatments with increasing zinc levels (T1, control, 85 mg Zn kg-1; T2, 105 mg Zn kg-1; T3, 125 mg Zn kg-1 and T4, 145 mg Zn kg-1). The findings showed that the dietary zinc addition had a positive outcome on the SGR, WG, FCR, PG and CF values of juvenile carp. For all parameters studied, the best results were found in the juveniles fed T2 (105 mg Zn kg-1), but the significantly lowest growth (P < 0.05) was obtained in juveniles fed the basal diet containing 85 mg Zn/kg-1. The findings also showed that 105 and 125 mg Zn/kg-1 diet caused significantly higher FCR, SGR and average daily weight gain (ADG) in comparison to those fed with diets containing 85 and 145 mg Zn/kg-1. In addition, feed intake was raised with increasing dietary zinc amounts up to 105 mg/kg-1 diet. In the antioxidant study, even though the SOD and CAT analysis results did not show a linear increase in the increasing Zn ratio in the diets, higher values were obtained compared to the control groups. SOD highest values in T3 for liver (0.713±0.220) and T1 for muscle (0.751±0.144), CAT values highest in T2 for liver (0.849±0.115) and T2 for muscle (1.059±0.148) was obtained. MDA values were completely higher for the muscle than for the control group, and for the liver, a lower value was obtained in the T2 trial group than the control group (1.671±0.230). In conclusion, this study confirms the positive effects of the use of 105 mg of Zn in diets to enhance growth performance of carp juveniles. In addition, SOD and CAT analysis results also confirm the positive effects of using 105 mg Zn in the diets to increase the growth performance of juvenile carp in this study. The findings of the present study will help scientists; fish feed producers and fish farmers to optimize dietary Zn concentrations for juvenile carp. The findings of this study will assist scientists; fish feed manufacturers and fish breeders in determining dietary Zn concentrations for juvenile carp. Keywords: Carp feed, Feed Conversion Rate, Zinc, Nutrition, Proportional Growth, Antioxidant, Cyprinus Carpio