Agressive toward baby

[sugarmouse]

I have a 7month old Staffi X pup that we got from a rescue center (we've had her for 3mths) She is a very excitable, lovable, playful puppy but you would not call her agressive at all. She is too lively around young children and tends to knock them down and hurt them in her zeal to play with them. We have been putting her in her cage/bed in the kitchen when very young children come to visit, and she tends to cry to get out.

Today while my sister was visiting with her 18mth old, the baby went over to the cage (which she has done before with no reaction except for our dog to wage her tail and try and like the baby's fingers) but today our puppy growled, bared her teeth and tried to bite at the baby through the cage. I am very concerned and would like any advice on how to curb this behaviour in our dog and/or insight into anything we are doing that needs changing or should be doing and aren't.