Oh, and looks like you really didn't need pubmed, even Wiki has the weanling pigs.
http://en.wikipedia.org/wiki/Oligosaccharide
The same article also says that oligoblah is a simple sugar though. Wouldn't this mean that it would highly likely be eaten by the yeast and not be left behind like the more complex sugars? Not that I fully trust wiki...
Actually an oligosaccharide is a complex sugar/carbohydrate made up of 3-10 simple sugar molecules. Oligo is latin or greek for many. The wiki article is confusing.
Here's oligosaccharide molecule
and now a simple sugar (glucose):
Your GI system needs to break the oligosaccharide down to its simple sugar components in order to digest and absorb it. More work = more "distrubance."
Edit, I thought I posted some images of molecules. Guess I don't have this internet thing worked out yet! Anyway, oligo is a large molecule and simple is small.