
Some males do just have a stronger odour than others, and 'marking' smells alot stronger than urintating when they are entire...
I would get a vet check,not to panic ;) but just to eliminate that it *could* be due to a Unrinary tract infection.
(The cause being feed, would be lower on my list of possibles, if that helps ;) )
Good luck and I'm sure you'll get more advice/ideas coming along soon.. :D