Dipping cattle in a vat provided with splashboards set at the proper angle destroys most of the hornflies present on the animals.
"Special Report on Diseases of Cattle"
U.S. Department of Agriculture J.R. Mohler
Unless the splashboards are used all but a few of the flies succeed in escaping as the cattle plunge into the bath and later return to them.
"Special Report on Diseases of Cattle"
U.S. Department of Agriculture J.R. Mohler