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
The need of vitamins for animals and their importance to proper growth and health has been so thoroughly propagandized that we are beginning to feel justified in feeding fish to cattle and parsnips to dogs. Our herbivorous animals are being fed meat and carnivorous animals vegetables to supply their vitamin. requirements.
Taylor, E. P.
"Vitamins and Their Relation to Horse Feeding,"
Iowa State University Veterinarian: Vol. 2
, Article 16.
Available at: http://lib.dr.iastate.edu/iowastate_veterinarian/vol2/iss2/16