I can't find any information for the dog...

[JMeJ]

Do I feed it animal feed? Do I let it out of the house as soon as I get him? I can't believe how hard it is to find this information.

[Maya-Neko]

There aren't any informations, because there isn't that much to know about. Just take him onto your arms once a day and feed him (animal feed, as it's the most obvious thing to give him if the game doesn't tell you anything else) to raise friendships. You want to have full hearts at the dog races. He doesn't serve anything beyond this.