Originally posted by Twisterdog

Culling generally refers to newborn puppies. Puppies are generally culled if they show obvious birth defects or health issues, albeit some breeders do cull for deafness or mismarks. It would therefore not be possible the "cull" a sheltie pup for being too large, as the breeder wouldn't really know the dog's full size until it is over six months old.
Yeah, generally is the term. But that wasn't always the case. As I said, it wasn't considered appropriate to have a large sheltie, and an embarrassed owner might cull one, adult or not. In the case of dogs that need to work for their food, if an adult dog shows poor working ability, then they would cull it. Technically culling doesn't always mean killing, so I'll state the technical, however obvious; they would take it out back and shoot or drown it. Luckily it is no longer considered appropriate in our society.