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 July 23, 1959, a call was received from a client Wll0 reported that his hogs were sick. Upon arrival at the client's farm, two dead pigs were found. Three other pigs were weak and when forced to move, did so at a staggering gait. These pigs were examined. The temperatures ranged from 101.5° to 102.7,° well within the normal range. Olle pig was noted to be breathing rather rapidly and evidence of a watery diarrhea was noted on all of the affected pigs. One of the pigs was unable to rise. A slight dilation of the pupils was noted.
Wunder, R. D. and Schultz, R. A.
"Nitrate Poisoning in Swine,"
Iowa State University Veterinarian: Vol. 22
, Article 10.
Available at: https://lib.dr.iastate.edu/iowastate_veterinarian/vol22/iss2/10