Hi XXXXXXXX,
'If there were more than one tie then she will have a mix of puppies. Even though you did not see her and the desired dog tie, sometimes it can still happen if the male tries to mount but does not tie inside her, it's called a slip mating.
Now generally you would wait until the bloody discharge is done before mating because the bloody discharge means she is in the first stage of heat so she may not be willing to take to another dogs advances in that stage. Once that bloody discharge stops and you see a pale yellow discharge , then this is the time you want to bring them together and there is a limited window of time to accomplish this. Anywhere from 4 to 9 days and this can also vary from dog to dog. Generally when the female is ready and in the second stage, she will put her tail to the side when the male approaches, this is called flagging. She may even move it to the side if you pet her hind end.
So it is possible the her window was short if she let one dog tie and now wants nothing to do with any other dog.
Gestation is usually around 63 day from a tie but you will still want to confirm pregnancy around day 25 with a sonogram because some dogs will go through a false pregnancy in the third stage of heat which will show all the same symptoms of a pregnant dog.
If she is pregnant the vet will probably suggest you change her food at a certain time so she has the energy to take care of the pups and he milk has enough protein for the pups to thrive on.
Here is more on the heat cycle of dogs. http://www.petplace.com/dogs/the-heat-cycle-of-dogs/page1.aspx
Here is a great site on pregnancy to how to care and prepare for a pregnant dog to how the pups are developing each week.
http://www.k9web.com/dog-faqs/medical/whelping.html#timeline-pups
dog training consultant
24 years training & behavior,pet first aide, Therapy dog eval., PA Animal Response Team
If both dogs mated her then you are going to have a mix of both of the dogs as the father, so there will be pups from both doners, but each pup will have one father.
There is DNA testing for dogs now so that may be an option for you.
Dogs can release multiple eggs and they can be fertilized by whichever dog's semen is present. If more than one male bred her, that's how many fathers the puppies can have. the main reason everyone gets a fair shot at the eggs is because the semen wait a day or two before fertilizing the eggs.
When a dog ovulates the eggs are not totally mature. They finish maturing as they enter into the uterine horns. Then whatever dog's semen is present releases from the uterine lining and heads for the eggs.
Now one single puppy cannot have two different fathers. Each puppy will get half of it's DNA makeup from Mom and one Father, but since often dogs have litters it's possible for two puppies from the same litter to have 2 different sires.