Why do cats and dogs become ill or die from melamine-contaminated pet food, but farm animals do not get sick from it?
Scraps of contaminated pet food that contained low levels of melamine were distributed to farms in a limited number of states and added to the feed consumed by hogs and chickens. These scraps made up only a small part of the total rations fed to farm animals, whereas pet food often constitutes the entire diet of cats and dogs, exposing them to more melamine. In addition, melamine is excreted in animal urine. When exposure levels are much higher, as was the case with cats and dogs, the melamine and its compounds appear to cause the formation of crystals in the kidney systems, resulting in kidney damage. There was no indication of kidney damage in farm animals. Both hogs and chickens known to have been fed contaminated feed appear to be healthy.
