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
Nutritional diseases as a result of inadequate amounts of calcium, phosphorus or vitamin D are not unusual in swine. The total amounts of calcium and phosphorus in the ration are significant and their relative amounts are equally important. In winter when pigs are kept stabled with a low intake of vtamin D the importance of the ratio of calcium to phosphorus in the ration assumes a more significant role. Data on amounts of calcium and phosphorus in swine serum, carcasses, milk and bones taken from the literature are summarized in Table 1. These data indicate that in the normal pig calcium is used in a proportion of about 1.6: 1 of phosphorus. The actual amount of a given mineral ingested by an animal is sometimes very difficult to determine. Average analyses as quoted by standard texts and various reports are useful guides but in some cases may be misleading.
Eveleth, D. F.
"The Importance of Calcium and Phosphorus in Swine Rations,"
Iowa State University Veterinarian: Vol. 1
, Article 5.
Available at: http://lib.dr.iastate.edu/iowastate_veterinarian/vol1/iss1/5