Maybe the fact that both words refer to extremes has led to the mixup

Quite true, wsieber, but the owner of this Liverpudlian pound, which is not to be confused with a British pound, is more concerned with his breeds getting mixed up in each others ends than with any mixup in the ends to which you refer -- altho a "bastard", as you duly note, is the result in either case.

At Battersea Dog Home, making ends meet never results in a "bastard" -- which is what this fuss is all about.

Red the Lurch is making a laughingstock of their livestock.