Is this a joke?
You have a 5-yr-old tiger with huge prey instinct and you worry about a new dog hurting the cat?!?
However, if you do
have a 5-yr-old tiger with a huge prey instinct, introducing it to a dog would likely have dire consequences for the dog...no matter how big, what breed or what age...
"We are--each of us--dying; it's how we live in the meantime that makes the difference."
"It's not what you gather, but what you scatter that tells what kind of life you have lived!"
"Be kinder than necessary, for everyone you meet is fighting some kind of battle."