AN EVALUATION OF THE POTENTIAL EFFECTS OF IVERMECTIN ON THE DECOMPOSITION OF CATTLE DUNG PATS

The parasiticide ivermectin has been administered to domestic livestoc k since 1981 to control internal and external parasites, including ins ects; some of the ivermectin is excreted unchanged in faeces. Concerns over the effects of ivermectin on dung-utilising insect populations a nd the potential for consequent persistence of dung on pastures have b een raised. This paper presents the results of a study over two grazin g seasons of the rate of decomposition of cattle dung pats exposed to normal environmental influences. The cattle had been treated at therap eutic levels with either an injectable or a sustained release bolus fo rmulation of ivermectin. It was concluded that the rate of decompositi on of the dung pats, the extent of their avoidance by the cows, the or ganic matter content of the soil and the populations of earthworms in the pastures were not affected by the use of ivermectin.