There is a slight slight difference in his pronunciation of daddy when there are dogs around but it takes a parental ear to hear the minute detail in his voice. A few years ago, our friends had a list of their son's words and associated definitions listed up on their fridge. Balloon meant tomato and such. Right now, our fridge defintiion list would consist of one word with multiple meanings.
Daddy = daddy, doggies, mommy, person walking on the street, shiny object in the elevator and anything else I happen to see when my mouth is moving.
He is babbling other words and seems to increase in his "conversations" when he is with other kids so for the moment, I have very fun conversations with him during the day in which I just make up our own stories.