Trying to decide which of the adorable puppies in a mixed breed litter is meant for you isn't easy. It's especially difficult if each puppy boasts a unique look. While puppies in the same litter can't be different pure breeds, they can have different fathers.
Superfecundation is the technical term for litters sired by more than one father. It doesn't just occur in dogs and cats -- although rare, it's even possible for fraternal human twins to have different dads. If two purebred dogs mate but some of the resulting litter are obviously not that breed, the owner can figure there's another sire somewhere. It's harder if there are multiple sires without DNA testing. Sometimes it's guesswork. If the mother is a beagle and some of her pups look like German shepherds and others boast poodle-type hair, she might have had a few boyfriends.
How It Happens
When a female dog goes into heat, she can remain receptive to breeding for seven days or more. If she mates with more than one dog during that roughly week-long period, puppies in the litter might have different sires. While few people intentionally breed a female dog to more than one male, multiple fatherhood can easily occur if a dog in heat escapes the confines of her house and yard and meets up with various males. Because of a canine's super-strong sense of smell, intact male dogs on the loose don't have difficulty locating the whereabouts of females experiencing estrous. Female dogs leave clues as to mating availability in their urine. If your dog in heat gets loose and you've lost sight of her, even for a short time, take her to the vet when she gets back. Your vet can conduct tests, such a vagina smear to detect sperm.
Puppies with different sires can't be different breeds, but there's a possibility that some might be purebred and others so-called "designer dogs." For example, if a cocker spaniel female mates with both a purebred cocker spaniel and a purebred poodle, her cocker spaniel puppies are purebreds. The pups with the poodle parentage are cockapoos, or cocker spaniel/poodle crosses. While they aren't purebred, certain crosses are well-known and relatively consistent in size and appearance. Other well-known hybrids include the "puggle" -- a beagle/pug cross or poodles crossed with various breeds, resulting in "oodles." These include labradoodles, or Labrador retriever crosses; goldendoodles, or golden retriever mixes, and schnoodles, a poodle/schnauzer pairing.
Multiple-Sired Litter Registration
Since DNA testing became readily available, determining parentage is no longer a matter of educated guessing. As of 1998, the American Kennel Club permits registration of litters sired by more than one dog. To qualify for testing, the breeder must obtain DNA kits from the AKC for all potential sires, as well as the mother and every puppy in the litter. Taking samples is simply a matter of cheek swabbing and returning the swabs to the AKC. If the two potential sires are related, such as full brothers, additional testing might be necessary. After the AKC determines the correct sire of each puppy, the breeder can then submit the application for litter registration.
Jane Meggitt has been a writer for more than 20 years. In addition to reporting for a major newspaper chain, she has been published in "Horse News," "Suburban Classic," "Hoof Beats," "Equine Journal" and other publications. She has a Bachelor of Arts in English from New York University and an Associate of Arts from the American Academy of Dramatics Arts, New York City.