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
During the past 30 years the importance of the male in problems of reproduction has been re-evaluated and with the development of artificial insemination has come to be regarded with equal or even greater concern than the importance of the female. There are many references to support the view that the bull might be an active spreader of genital infections which may temporarily or permanently impair the fertility of infected females.
Lovell, James E.
"A Discussion of Seminal Vesiculitis in the Bull,"
Iowa State University Veterinarian: Vol. 19
, Article 1.
Available at: http://lib.dr.iastate.edu/iowastate_veterinarian/vol19/iss2/1