FDA has received reports that products containing colloidal silver are being promoted for use in the treatment of mastitis and other serious disease conditions of dairy cattle, as well as for various conditions of companion animals. For example, FDA’s Center for Veterinary Medicine has received reports from the Agency's regional milk specialists and State inspectors that colloidal silver products have been found on some dairy farms.
Bagley, Clell, "Colloidal Silver Not Approved for Treating Animals" (1997). All Current Publications. Paper 456.