My female has had 3 litters in the past. We use to have the stud dog on our property so trying to pin point the breeding time was not an issue. The last 2heats were not successful breedings, I thought I had "missed" the ovulation time. We've tried 2 different stud dogs, the female stands for them but the dogs do not tie up and there is no litter. This is the 3rd breeding attempt, the 3rd heat and we've had a stud dog here from day 8 of her heat until today which is the 13th day still the stud dog does not try to long and doesn't tie up. The female is standing for him and has her tail to the side. What is the problem? I don't get it? The stud dog has bred in the past too??