Anonymouse:
Well, Pratchett has given us the possibility of dwarfbread, with all the nutritional value and edibility of gravel 
Even though cannibalism could be a viable option (in the old fluff, when they were trapped underground afaik) or even subterranian plants, fungi and animals, ‘normal’ food obtained by either trade or raids seems the most logical option. There must be vast fields where slaves toil day-in-day-out, with supply trains rolling non-stop towards the CD settlements.
