Effects Of Residues Of Ivermectin In Cattle Dung On The Dung Arthropods In A Typical Steppe Of Inner Mongolia

The typical steppe of Inner Mongolia is an important part of grassland ecosystem in China.Ivermectin is widely used in animal husbandry due to its efficient action on a variety of nematodes and in vitro parasitic arthropods.Most of the medicine is excreted in the pasture after cattle are grazed with Ivermectin.The residue of Ivermectin in livestock feces may have direct and indirect effects on the dung arthropod community and dispersal of dung pats in typical grassland in Inner Mongolia.From July to October 2018,the experiment was carried out on the family grazing grassland in Haoltugaole town,Xiwu banner,Xilingol league,Inner Mongolia.10 adult Mongolian cattle weighing about 450kg were divided into2 groups according to the 5 head group.The treatment group was treated with0.2 mg/kg body weight of Ivermectin orally,while the control group was not treated with Ivermectin.Fresh dung samples of the two groups were collected at 3 and 7day after treatment.In July 2019,fresh cattle dung without drug treatment was collected and added with an appropriate 0.3%Ivermectin solution to produce samples with residual concentrations of 0,2.5,5,10 and20 mg Ivermectin/kg of fresh cattle dung,which were respectively called C₀,C₁,C₂,C₃ and C₄.The effects of Ivermectin residues in cattle dung on the community dynamics of fecal arthropod and the decomposition of dung pats were investigated by means of artificial stacking.The results of this study can provide a basis for the evaluation of the ecological effects of Ivermectin routine use in typical temperate steppe and the rational use of Ivermectin in disease and insect control of grazing cattle in the study area.The main research results are as follows:1.Ivermectin residue in cattle dung reduced the community abundance of arthropods by 70.5%and the number of groups by 40.3%compared with the control feces?P<0.05?.The community evenness index?J?was significantly increased?P<0.05?,but the diversity index?H'?and dominance index?D?were not significantly affected.The influence rule on dung arthropod functional groups was that saprophagous>predatory>phytophagous>omnivorous,the abundance of the first three functional groups in dung pads of Ivermectin treatment was significantly lower than that of the control dung pads?P<0.05?.The abundance of two functional groups of Coleoptera decreased significantly?P<0.05?,among which groups with weak ossification on body surface?mainly beetle larvae?were more sensitive than groups with strong ossification on body surface?mainly beetle adults?.2.The residue of Ivermectin in cattle dung led to a significant decrease in the abundance of gamasida,Actinetidida,Collembola,Staphylinidae and dung beetle dominant species,while a significant increase in the abundance of Oribatida?P<0.05?.3.The residue of Ivermectin in cattle dung causes slow dispersal of cattle dung.The water content and organic matter content of the treated dung were significantly higher than that of the control dung?P<0.05?.The pH of dung pats was significantly lower than that of control dung pats?P<0.05?.4.The effect of cattle dung in the 3 day after the drug was greater than that in the 7 day after the drug,and the effect lasted for 2 months or longer after the drug was excreted.5.There was no linear relationship between dung arthropod abundance and Ivermectin concentration,and the arthropod abundance showed the rule of C₂>C₀>C₁>C₄>C₃.In conclusion,the routine use of Ivermectin by grazing livestock can significantly reduce the community abundance and group number of dung arthropods in typical grasslands in Inner Mongolia,delay the dispersal of dung pats,and indirectly affect the grassland ecosystem.