Preliminary Exploration On Soil Ecotoxicology Of Maduramicin

Maduramicin is a polyether ionophore antibiotic,which is particularly used for the prevention and treatment of coccidiosis in poultry.Intensive animal production mode has led to much concentrated use of maduramicin.While maduramicin is mainly excreted in its original form through feces,it will inevitably affect the ecosystem.In this study,the effects of maduramicin on soil ecological environment were studied from three aspects:soil microorganisms,vegetables and earthworms.The main test results are as follows:In the range of 5 to 20 mg/kg,soil ammoniation was significantly increased in a dosedependent manner,and soil nitrification was significantly inhibited,while soil respiration had no significant effect.In addition,the activities of soil urease,alkaline phosphatase and sucrase were not effected during the 14-day test period.On the 14th day,10 mg/kg maduramicin significantly inhibited the activity of soil dehydrogenase,and 20 mg/kg maduramicin significantly promoted the activity of soil catalase.Three widely grown and eaten vegetables,tomato,radish and Cabbage,were selected for seed germination test.In the range of 5 to 20 mg/L,maduramicin had no effect on seed germination percentage and seedling root elongation,but plant weight and stem and leaf length decreased significantly in a dose-dependent manner.In addition,under the treatment of 20 mg/L maduramicin,the germination of three kinds of vegetable seeds showed lodging,blackening and stem curling.The sensitivity of three kinds of vegetables to maduramicin was ranked as cabbage>radish>tomato.Therefore,we chose cabbage to continue the pot experiment.The plant weight,stem and leaf length,root length and antioxidant enzyme activity of cabbage were measured at the 10th,20th and 30th days,respectively.The results showed that maduramicin had no effect on the growth and development indexes of Cabbage at the 10th day,but the plant weight at the 20th and 30th days decreased significantly under the treatment of 10 and 20 mg/kg maduramicin.However,the stem and leaf length decreased significantly under the treatment of 20 mg/kg maduramicin,while the root length had no significant change during the whole test period.The activity of antioxidant enzymes in Cabbage showed a siguificant trend on the 10th day,that is,the activities of peroxidase(POD)and catalase(CAT)increased,and the activities of superoxide dismutase(SOD)decreased.The 14-day LD50 of maduramicin against Eisenia foetida was 32.462 mg/kg.There was no death in earthworms at 20 mg/kg in the acute toxicity test,so the maduramicin concentration was set at 5,10 and 20 mg/kg for subsequent tests.In the presence of 10 and 20 mg/kg maduramicin,extremely significant avoidance was observed in earthworms.The growth and reproduction of earthworms were significantly inhibited within 28 days of maduramicin exposure.The activity of POD in earthworms was significantly increased under the treatment of 10 and 20 mg/kg maduramicin,and the activity of CAT was significantly increased under the treatment of 20 mg/kg maduramicin.There was no significant effect on the activity of SOD.Malondialdehyde(MDA)content only increased significantly in the presence of 20 mg/kg maduramicin on the 21st day.The expression of CAT gene in earthworms was significantly up-regulated,the expression of HSP70 and TCTP genes was first down-regulated and then up-regulated,and the SOD and ANN genes had no significant effect.The above results showed that maduramicin affected the activity of soil microorganisms.It inhibited the growths of tomato,radish and Cabbage and caused oxidative damage to Cabbage.It has negative effects on the growth and reproduction of earthworms and causes oxidative damage ang stress to earthworms.