Our neighbour (farmer) once had a female Bernese mountaindog and one morning was faced with quite a few dangerous males that broke through their double-glazed kitchen windows to get to their bitch in heat. Dangerous males, because they were not trained or educated whatsoever and attacked our neighbour when trying to intervene and get the strange males out of the house. It turned out they came from as far as more than 25 km away and their owners did not care.
Needless to say that some of them were successful and some 63 days later the female had 14! mixed puppies.
We had similar experiences when owning two intact females, but were lucky to scare and fight these uncontrolled males off, so no puppies here.
But ever since we only have males.