Offspring from a mother-son mating would, therefore, have a 25% chance of inheriting two bad copies of the mutations that have been passed down to the son. This is a greater than 100-fold risk compared to an outbred dog! Inbreeding in dogs has real consequences.
Other negative effects of inbreeding documented include decreased immune system function, decreased viability, decreased reproductive ability and the loss of genetic diversity (i.e. decrease in genetic variation). Collectively, these adverse effects of inbreeding are known as inbreeding depression.
Severe separation anxiety, impulsive behaviors (compulsively chasing vehicles or running out into the street), fearfulness, and even a complete lack of affection for their human family are all more common in inbred dogs. While many dog breeds have high degrees of inbreeding, some are worse than others.
The average COI for purebred dogs is ~20%. Specific breeds can be higher or lower than this value. For some breeds, the average coefficient of inbreeding can approach or even pass 40%. Because these are average numbers, individual COI can vary.
Shorter Life Span
With all the complications we have mentioned so far, no wonder inbred dogs have shorter life spans as compared to outbred ones. Research conducted in the Bokyo Lab shows that there is a 6 to 10-month reduction in lifespan for every 10% increase in inbreeding.
Inbreeding two closely related dogs can cause malfunctioning organs, cosmetic defects, and other abnormalities. While some congenital disabilities are manageable, others pose lifelong trouble for the dog. Many pedigree dogs born with any flaw are considered defective, so they won't be eligible for registration.
They found that on average, the more inbred an animal was (using its “true COI” measurement), the smaller the litter size. The least inbred dogs had an average litter size of 8 puppies, while the most inbred dogs had an average litter size of 6-7 puppies.
The highest level of inbreeding by far (> 80%) is for the Norwegian Lundehund. This breed suffers from extremely low fertility and high puppy mortality as well as an often lethal gastrointestinal disorder.
Astoundingly, the Devils Hole pupfish is so inbred that 58% of the genomes of these eight individuals are identical, on average.
Most modern dog breeds were established within the last 200 years. Through the use of studbooks to ensure pure-bred pedigrees in the last 100 years, inbreeding has become the norm in many breeds.
Offspring from a mother-son mating would, therefore, have a 25% chance of inheriting two bad copies of the mutations that have been passed down to the son. This is a greater than 100-fold risk compared to an outbred dog! Inbreeding in dogs has real consequences.
Genetic coefficient of inbreeding (COI) is the most accurate method for measuring inbreeding. Unlike pedigree based COI calculations, genetic COI evaluates the actual pieces of DNA in your dog to identify which proportion traces back to inbreeding.
Studies have confirmed an increase in several genetic disorders due to inbreeding such as blindness, hearing loss, neonatal diabetes, limb malformations, disorders of sex development, schizophrenia and several others.
Inbreeding is a double-edged sword. On the one hand a certain amount of inbreeding can fix and improve type to produce excellent quality animals. On the other hand, excessive inbreeding can limit the gene pool so that the breed loses vigor.
Inbreeding reduces the genetic variation within that breed or population. Inbreeding has been a common practice in companion animals (and other domesticated species) as it increases the likelihood that animals will share desired traits such as their physical characteristics because they are genetically similar [1, 2].
Not all dog breeds are alike in terms of health, however. Tamaskan Dogs, Barbets, Australian Labradoodles, Danish-Swedish Farmdogs, Mudis, and Koolies were some of the least inbred, and they had rates of vet care comparable to mixed-breed dogs.
Introduction. Mating with relatives (inbreeding) can result in offspring with reduced survival and fertility, a phenomenon known as inbreeding depression [1]. Inbreeding depression has been observed to occur in wild animals with severe consequences [2,3].
Inbreeding increases the risk of recessive gene disorders
Inbreeding also increases the risk of disorders caused by recessive genes. These disorders can lead to calf abnormalities, miscarriages and stillbirths. Animals must have two copies of a recessive gene to have the disorder.
If a dog is extensively inbred, it will likely have a shorter life. And how about spaying and neutering? They impact your dog's life span too, by giving him (or her) protection from certain kinds of cancer.
These data show that most breeds of dogs are highly inbred, with average values that exceed the inbreeding level that results from the mating of half-siblings (12.5%).
The most obvious effects of inbreeding are poorer reproductive efficiency including higher mortality rates, lower growth rates and a higher frequency of hereditary abnormalities. This has been shown by numerous studies with cattle, horses, sheep, swine and laboratory animals.
Smaller populations become inbred more quickly, so the simplest way to reduce the rate that inbreeding is to maintain a larger population of breeding animals. The easiest way to do this without producing an oversupply of puppies is to increase the number of different sires being used in breeding.
Inbreeding puts dogs at risk of birth defects and genetically inherited health problems.
On most occasions, it is generally considered dangerous to breed brother and sister dogs together. This is because of the risk of long-term health complications. Even if inbreeding is carefully planned and managed, it still has the potential to cause other indirect problems over time.
Keep Your Dogs Separated to Prevent Mating
This can be done by keeping them in separate rooms where they cannot see each other, tying them away from one another, keeping the female dog in an enclosure, or leaving the female dog in an outdoor enclosure that is cool, safe, and secure.