Just like the theory of relativity, it seems so obvious once you hear it. But some smart doggy had to figure out that a dog's energy to perform a trick (e) = the mass of the treat (m) x the speed of the delivery of the treat (c). This may break down when you get to the quantum canine physics level (don't get us started on dark treat matter), but this formula is surely worth a Nobel Prize in canine theoretical physics.  
As with any of our shirts, this isn't intended to be a shirt for dogs, but you never know if newly intelligent and self-aware dogs will want to continue to run around naked with their privates hanging out, so let's just leave it up to them. Whoever wears this will love the 100% combed, ring-spun cotton, and the tear-away label to keep the back itches away.
These shirts tend to run a little on the big side, which will either leave you room to grow or you can pick a size down if needed.