In the days before computers, I kept a book (now its all carefully entered in to special folders on the 'machine' and provides me with a complete history) - total sickness record, including jabs and innoculations (and cost of pills / treatment), of each dog. Weight at birth of puppies, ease of whelping. Onset of seasons, boys starting to react (chuddering and showing interest), date relative to onset of color of the first time the girl's tail went over. Just about every aspect of each dog is carefully logged and catalogued.