Heh, I know this is a joke, but, I actually read a Can of Troll magic item somewhere or other.  
When you think about it, a D&D world makes provisioning an army a REALLY different thing.  Let's peruse our Monster Manual for a second shall we  ((Note, all this is of course campaign specific))?
- Animated Wagons for carting around your crap would be a HUGE thing and not that terribly difficult to make.
 
- Violet Fungus are medium creatures and grow in 2-12 days.  Evil armies might cart them around and feed captives to them creating easily transported food.
 
- Obviously undead armies/units have their own ...errr... feeding practices 

 
- Giant Beetles, particularly giant Fire Beetles would make an excellent food source
 
I'm sure there's more stuff out there.