Hunting

Nelly the cat was hunting this morning as I returned from my walk.  I watched her as she crept along the dyke stalking her prey.  The object of her attention was a butterfly which fluttered off as Nelly approached.  I thought butterflies were a nuisance to cats rather than a beast worthy of a hunt.
It has left me wondering whether we could breed a cat specifically to chase Cabbage Whites and prevent them from laying their eggs on my veg.