One of my friends returned from a vacation in Norway. I asked him if he was able to drink the milk there, and he said, no because all the milk there is חלב עקום - crooked milk, and the Gemarah prohibits Jews from drinking crooked milk.
I'm puzzled about this. It's the first time I have heard about this prohibition. I've been buying milk in cardboard cartons and when I pour it, the milk comes out at an angle. Is that what's considered "crooked" milk? Or maybe, it's a reference to milk that spoiled? Perhaps, I've been drinking traif milk all these years?
What exactly is considered crooked milk and why is it prohibited?