Utah State University Extension
A number of companies in the U.S. sell free-choice or cafeteria-style mineral supplements. Their rational is that ruminants will select the minerals they need and in the quantities they require for maintenance, pregnancy and growth.
Anderton, Laurel; McAvoy, Darren; and Kuhns, Michael R., "Native American Uses of Utah Forest Trees" (2012). All Current Publications. Paper 1212.