Monday, December 10, 2007 - 8:29 AM

The effects of veterinary parasiticides on the emergence of colonizing dung fauna and pasture quality

Daniel Skoczylas,, Holly Ferguson,, Douglas Walsh,, and Laura Corley Lavine, Washington State University, Department of Entomology, Pullman, WA

Dung fauna play an integral role in maintaining the health of ecosystems by breaking down fecal matter. The use of veterinary parasiticides may decrease the rate of decay of fecal matter by reducing population abundance of dung-dwelling insects. Dung-dwelling insects use fecal matter for nutrition and as habitat for mating and reproduction. Industry-wide adoption of ivermectin-like parasiticides has provided obvious economic benefits to ranchers. Our research investigates some of the non-target impacts that veterinary parasiticides have on survivorship of dung dwelling insects and the possible contribution of parasiticides to pasture pollution. Our studies were conducted using dung collected from cattle treated with veterinary parasiticides of the macrocyclic lactone class. Dung was collected weekly from treated cattle for up to eight weeks post treatment. Upon collection dung was placed into ziploc bags and stored at -20C. Dung was thawed and formed into 0.5 liter artificial pats that were placed in a pasture adjacent to where cattle were grazing. Dung pats remained in the field for five days, allowing dung fauna to colonize the dung pats. Pats were then removed from the field and placed in emergence buckets. Dung pats where monitored for insect emergence for 10 weeks. We report the impact that veterinary parasiticides of the macrocyclic lactone class have on colonizing dung-dwelling insects and the potential impacts parasiticides might have pasture quality in the Pacific Northwest.