I bred a "mini" cow out of my Milking Shorthorn once, bred A.I. to a Carnation Simmental bull (both animals peak at over 1100 lb. cows easily.
For some strange reason I got the smallest Frame 3 out of 10 score cow you've ever seen. I then bred her, believe it or not, to a Simmental
Fullblood bull and she threw......a small calf. I really should have just gone into the mini business. It was bigger money than the big cattle.
She calved, lil one, unassisted. I sold her shortly after with the calf. I wish I had kept photos.
Mini wise I'd pretty much stay away from them for all kinds of reasons, mainly genetic. But I understand that in Montana there are some really
progressive breeders that have "cleaned up" the genetics in small Herefords, for example. Dairy wise you've got dairy. That's all. If you're looking
for a small cow they're around, and you can view them in person, then buy.