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.