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
On May 7, 1952, a Jersey cow, 3 years old, was admitted to Stange Memorial Clinic with a history of having given birth to twins in October, 1950, one of which was alive at birth. At that time the cow suffered from retained placenta. The local practitioner had treated her for the retained placenta. She had not shown heat since birth of the twins. Estrogens were used in an attempt to induce heat, but they were ineffective.
"Pyometra in a Jersey Cow,"
Iowa State University Veterinarian: Vol. 15
, Article 12.
Available at: https://lib.dr.iastate.edu/iowastate_veterinarian/vol15/iss1/12