Another point being that a milking sow is not the most docile animal in the world. They do have tusks and they do know how to use them!

That said; there have been milking machines made for sows - I know that they were used in some research applications @ Cornell in the mid '70's.

I believe that there have historically been horse and camel cheeses made as well as the fermented drinks made from the milks.

And I seem to remember a case of dog's milk being used for infants in some tribe or another.....