Iowa State University Veterinarian Records, RS 22/6/0/9, University Archives, Special Collections Department, Iowa State University, http://www.add.lib.iastate.edu/spcl/arch/rgrp/22-6-0-9.html
Frequently bulls are encountered that refuse or are unable to serve a female or .an artificial vagina. Massage of the internal genitalia has been found to be an unsatisfactory way of obtaining semen. Semen collection by electroejaculation has been demonstrated in rams, boars and bulls. Failure of a young Guernsey bull at the Iowa State College Dairy Farm to serve a female or an artificial vagina prompted the development of a unit to collect semen by electrical stimulus. The instrument was designed by the Instrument Shop at Iowa State College.
"Semen Collection by Electrical Stimulation,"
Iowa State University Veterinarian: Vol. 17
, Article 4.
Available at: https://lib.dr.iastate.edu/iowastate_veterinarian/vol17/iss3/4