This article is from the Pet Owner's Guide to Common Small Animal Poisons, by Julie Dahlke, DVM, a graduate of the University of Minnesota, College of Veterinary Medicine.
Lead poisoning is seen occasionally in small animals, notably in
birds, frequently as a result of ingestion of a foreign object
containing lead, for instance, a toy, drapery weight, fishing weight,
lead shot or battery. However, it can also be seen with ingestion of
lead-containing paint, caulking, motor oil and other lead
sources. Clinical signs for animal suffering lead poisoning usually
include a combination of signs involving the gastrointestinal system
(vomiting, constipation diarrhea, painful abdomen) and the
neurological system (depression, blindness, circling, muscle tremors,
incoordination). Onset of signs is usually relatively quick but signs
can progress more slowly if the animal is slowly being exposed to the
poison, i.e., repeated ingestion of lead based paint.
Zinc poisoning occurs most frequently when dogs ingest zinc in the
form of pennies. The metal interacts with components of the animal's
red blood cells and can cause, weakness, trembling, loss of
appetite. Although not seen frequently, it is interesting to note how
such a mundane object can be toxic when ingested.