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
A three day old male Hereford calf was the object of a veterinary call this past summer. The history of the case was that the calf had nursed the first day after parturition, and hadn't nursed since. Examination revealed a congenital absence of the anal opening. Since there was no evident protrusion of the anal region, it was impossible to determine how far forward the posterior end of the tract was located. A disc of skin was removed from the region, but all efforts to locate the end of the rectum resulted in failure.
Wahl, R. C.
"Anal Atresia in a Calf,"
Iowa State University Veterinarian: Vol. 4
, Article 9.
Available at: http://lib.dr.iastate.edu/iowastate_veterinarian/vol4/iss1/9