Superman doesn't get ko'ed by nukes in canon books. not since the john byrne days.
it took a supernova exploding the planet he was standing on just to knock him unconscious recently.
DKR is not canon, and superman is nothing like he is nowadays in DKR.
krypto being a dog means he has none of the restraint that superman has, and you could even argue that his hearing and sense of smell are more acute than superman's. this being the same superman who can hear and smell in a vacuum.