What Happens When a Mother Dog Breeds With the Son?

For dogs, reproduction is controlled by hormones, not emotions. A female dog will enter a cycle where she is able to mate, called "going into heat," only two or three times per year. At that time, she releases hormones so powerful that an non-neutered male will respond with the desire to mate. For dogs, mating is so instinctual that a mother and son or father and daughter will just as easily mate as two unrelated dogs will. This close breeding introduces risks and problems later on.

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What Happens When a Mother Dog Breeds With the Son?
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Mother-son breeding outcome

What happens if a brother and sister dog have puppies? The mother can have puppies in this situation, but there is a risk that the puppies will have health problems. Breeders choose relatives to breed for the purpose of passing along good characteristics, but breeding closely related dogs can also pass along bad characteristics. There are formulas to help you determine the risks, but the actual outcome is often not known. Breeding Business says hip dysplasia and heart and liver conditions are common among puppies who are born from a mother-son union.

Inbreeding vs. line breeding dogs

The Royal Society for the Prevention of Cruelty to Animals defines the difference between inbreeding dogs and line breeding dogs. Inbreeding is the mating of close relatives. Line breeding dogs is a form of inbreeding, but it is accomplished by introducing more relatives to the pedigree so it is considered a milder form of inbreeding. When closely related dogs mate, it increases the chances of the offspring inheriting a serious genetic disorder. The more closely related the parents, the greater the chance of their offspring suffering from an inherited disorder.

Inbred dogs

When animals are closely related to each other, they have a greater likelihood of carrying the same defective genes. If these closely related animals mate, offspring inherits defective genes from both parents. Inherited diseases can occur that can cause serious health problems. Embark Veterinary explained that in a mother-son mating, the mother passes along 50 percent of her genome to each pup. That means each recessive mutation in the mother's genes has a 50 percent chance of being passed on to her son. The offspring of a mother-son mating, therefore, would have a 25 percent chance of inheriting two bad copies of the mutations that the son had inherited.

Genetic risks of dog inbreeding

A geneticist at the Tech Museum of Innovation explained that dogs have 39 pairs of chromosomes. The mother dog contributes one pair, and the father dog contributes the other pair. Parts of both chromosomes in a pair carry the exact same set of gene traits, which is why inbreeding can pass on genetic deficiencies to the offspring.

When working out the possibilities of dog genetic inheritance, this geneticist explained that there is no significant difference between the genetic risk in mating a mother to son versus father to daughter dog. The risks of inbred dogs are the same, and neither is desirable.

COI breeding

In dog genetics, there is a concept known as the coefficient of inbreeding, or COI. COI breeding takes into account the probability of inheriting two copies of the same allele (a form of a gene) from an ancestor that occurs on both the mother's side and the father's side. The Institute of Canine Biology gives an example of a COI of 10 percent, which would mean that the offspring has a one in 10 chance of inheriting two copies of the same gene. A low COI percentage indicates low genetic risk. A high COI would indicate a higher probability of health risks due to the dog inheriting two copies of the same gene from both parents. A COI of 10 percent is the threshold at which breeders recognize that the offspring will face serious challenges due to inbreeding.

AKC breeding age rules

The American Kennel Club has a guide to responsible dog breeding that places age minimums and maximums on breeding dogs. The male must not be less than 7 months old or more than 12 years of age at the time of mating. The female must not be less than 8 months or more than 12 years of age at the time of mating.