When I went to Canada a couple of years ago I had the rabies certificate, a certificate of good health that was less than 30 days old and an unopened bag of food. Turns out I didn't need any of that, but better safe than sorry. I'd travelled two states over to get into Canada and was heading to my dad's funeral with his ashes, so I didn't want to get turned around at the border. As it was, letting them know the purpose of my trip probably made it easier.