I dont know the truth to this saying but it is an old saying my great grandmother used to say and it definitely applied to all the women in my family.

"Big cow-no milk"

i believe it may be an italian wives tail..or something similar to that.

It just means that us big girls and those of us who have big breasts, will actually have no milk, or not enough to satisfy our babies so we have no choice but to put them on a bottle.