I believe Garvo limit feeds and wants room for all animals to eat at the same time; therefore, he uses 2 foot bunk space and 50 square foot per animal.  That would give you a 200x25 foot building for 100 head.  I don't limit feed so use 1 foot bunk space and 50 square foot per animal.  That gives a 100x50 foot building for 100 head.