Hello,
If you have experienced SLDS (Sudden Livestock Death Syndrome), symptoms of which include the animal dying without showing signs of illness, please post here describing the event and, if possible, show the pedigree bars so we can investigate the possibility of a bug.
Known list of bugs animal-related:
Sometimes baby goats and baby cows drop pig snouts, pork racks, hams, and other pig-related items when butchered.
Sometimes if you gather lard a pig, it gives lard. If you click gather lard again, the pig disappears.