Effects of dietary manganese amount on growth and antioxidant activities of sub-adult Litopenaeus vannamei

ObjectiveSuitable dose of dietary manganese(Mn)supplementation for sub-adult Litopenaeus vannamei was studied to provide scientific basis for the formulation of L.vannamei compound feed.MethodWith MnSO4·H2O as source of Mn,six Mn supplementation doses were set:0(control),50,100,150,200 and 300 mg/kg.Sub-adult L.van-namei(initial weight 4.83±0.39 g/shirmp,initial body length 8.23±0.43 cm/shirmp)was fed different diets for 10 weeks, then growth performance and antioxidant activity were determined.ResultMn supplemental doses had insignificant dif-ference(P>0.05,the same below)on survival rate of L.vannamei.Weight gain(WG)and specific growth rate(SGR)of Mn treatment groups except for 50 mg/kg treatment group were significantly(P<0.05,the same below)higher that of the control,and 200 mg/kg treatment group presented the optimum effects.Activities of Mn-superoxide dismutase(Mn-SOD)and total-superoxide dismutase(T-SOD)in serum and hepatopancreas increased firstly and then went down with the in-creasing of Mn supplemental dose.Activities of Mn-SOD and T-SOD in serum and hepatopancreas were significantly higher than control group when Mn supplemental doses were 150 and 200 mg/kg;but activities of Mn-SOD and T-SOD reduced when Mn supplemental dose was 300 mg/kg.Response of total antioxidant capacity(T-AOC)in serum and hepatopancreas of L.vannamei to dietary Mn supplemental dose was consistent with activities of Mn-SOD and T-SOD,and the optimal supplemental range was 150-200 mg/kg.Mn supplementation did not significantly affect malondialdehyde(MDA)content in serum,nor did it significantly reduce MDA content in hepatopancreas.When Mn supplemental dose reached 300 mg/kg, MDA content in hepatopancreas was significantly higher than other Mn treatment groups and control group.ConclusionAppropriate Mn supplementation in feed can promote the growth of sub-adult L. vannamei and increase T-AOC by in-creasing SOD activity.But excessive supplementation of Mn in feed may restrain the antioxidant activity of sub-adult L. vannamei at a certain extent,and lead to damage of hepatopancreas.According to the indictors of growth performance and antioxidant activity,the suitable range of Mn supplemental dose for sub-adult L.vannamei is 150-200 mg/kg.