{"id":15350,"date":"2019-06-12T18:07:53","date_gmt":"2019-06-12T18:07:53","guid":{"rendered":"http:\/\/labgenvet.ca\/?page_id=15350"},"modified":"2025-09-30T15:16:26","modified_gmt":"2025-09-30T15:16:26","slug":"dog-genetics-4-0-evolution-breeds-breeding-strategies-and-inbreeding","status":"publish","type":"page","link":"https:\/\/labgenvet.ca\/en\/dog-genetics-4-0-evolution-breeds-breeding-strategies-and-inbreeding\/","title":{"rendered":"Dog Genetics 4.0: Evolution, Breeds, Breeding strategies and Inbreeding"},"content":{"rendered":"

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Dog Genetics 4.0: Evolution, Breeds, Breeding Strategies and Inbreeding<\/h1>\r\n

 <\/p>\r\n

The Evolution of Dogs<\/h3>\r\n
\"\"<\/a>
Grey Wolf<\/span><\/div><\/div>\r\n

The dog (Canis familiaris<\/em><\/strong>, or Canis lupus familiaris<\/em><\/strong>) is a multiparous carnivore.\u00a0 Its genome consists of 2.4 billion bases organized on 39 pairs of chromosomes, plus one mitochondrial chromosome.<\/p>\r\n

The dog holds the title of the first animal domesticated and even the only animal domesticated before the dawn of agriculture.\u00a0 A common ancestor of the dog (Canis lupus familiaris<\/em>) and the gray wolf (Canis lupus<\/em>) diverged between 15,000 and 32,000 years ago to give rise to these two lineages.\u00a0 According to one theory, the event that precipitated the evolution of the wild wolf into the modern dog was the change in its behavior towards humans. The ancestor of the dog (\u201cprotodog\u201d) lost its fear of humans, which allowed it to live alongside humans and gain access to new food sources.\u00a0 This change in behavior was necessary to establish this favorable relationship with humans.<\/p>\r\n

It is important to consider a few points concerning the genetics of the gray wolf and the domestic dog.\u00a0 The dog is not a different species from the gray wolf, but rather a subspecies.\u00a0 This is proven by the fact that dogs, wolves, and even coyotes, despite having different physical characteristics and behaviors, have the same number of chromosomes (78) and can successfully reproduce with each other.\u00a0 There are some differences in their genomes, but the genetic similarities are even more numerous and striking.\u00a0 The year and place of the first domestication of dogs have not yet been confirmed, but recent discoveries seem to show that several early domestication events (two, three, or even more) took place in different locations in Europe and eastern Siberia.\u00a0 Advances in archaeological and genetic research will continue to clarify the sites and dates of dog domestication.\u00a0 It should be noted that the exact subclass of gray wolf that gave rise to the dog no longer exists; it is extinct.<\/p>\r\n

<\/p>\r\n

Natural breeds and village dogs<\/h3>\r\n

With the advent of agriculture and the migration of our ancestors from caves to villages, the domestication of dogs continued. Dogs were useful to humans as sentinels, guards, hunting companions, draft animals, shepherds, and, of course, companions and sources of entertainment. Through (relatively) natural selection in the environment, geographical isolation, and the tasks expected of them, these village dogs developed into traditional types of dogs, known as \u201cnatural breeds\u201d or \u201clandraces.\u201d\u00a0 These natural breeds include, among others, herding dogs, hounds, mastiffs, spaniels, terriers, and lapdogs. These breeds of dogs developed primarily for the function the animals were required to perform and involved selection of both favorable behaviors and physical characteristics to promote the animal\u2019s utility to man.\u00a0 It is these natural breeds that became the basis for what are now known as the purebred dog breeds. The emphasis once placed on the animal’s function is still reflected today in the organization of modern purebreds in various national and international kennel clubs. For example, the American Kennel Club (AKC) groups purebreds largely according to their ancestral utilitarian functions: herding dogs, hunting dogs, working dogs, sporting dogs, non-sporting dogs, terriers, miniature dogs, and then the catch-all miscellaneous dogs.<\/p>\r\n

The Development of the Purebred Dog<\/h3>\r\n

\"\"<\/a>It is only very recently in the human-dog relationship that purebred dog breeds were developed.\u00a0 Over the last 200 or so years, amateur dog breeders used the examples offered by poultry and cattle breeders to form dog breeding clubs.\u00a0 This initially involved extensive crossbreeding between particular foundation breeds of dogs to place the desired traits within a small number of individual animals.\u00a0 What followed was intensive inbreeding of these animals in order to fix the traits in question.\u00a0 These desirable traits were based on a combination of physical and behavioral characteristics as well as on novelty.\u00a0\u00a0<\/p>\r\n

Defining Dog Breed Characteristics<\/h3>\r\n

\"\"<\/a><\/p>\r\n

It is only recently in history that modern purebred dog breeds were developed. Over the past 200 years, amateur dog breeders in England followed the example of poultry and cattle breeders to develop dog breeding clubs. This also marked the beginning of crossbreeding between different dog breeds in order to create mixtures combining several desirable characteristics from different breeds in a single dog. This was followed by an intense wave of breeding among a small number of dogs of the same lineage (inbreeding) with a view to fixing desirable traits in the breeding stock. These desirable traits were based on a combination of physical and behavioral characteristics and on the uniqueness of the animal’s attributes.\u00a0 Pure breeds were defined by breeding clubs, using a description of desirable and undesirable traits and characteristics and a master pedigree or stud book.\u00a0\u00a0 In the beginning, the pedigree book was open, and all dogs that met the breed definition and criteria set by the breeding clubs were considered purebred.\u00a0 At a certain point, the pedigree book was closed.\u00a0\u00a0\u00a0 From that point on, in order to register an animal in the book, both parents of the animal in question had to already be in the book.\u00a0\u00a0 The Kennel Club, founded in England in 1873, was the first dog club to formalize the entire procedure for documenting the descriptions and pedigrees of different breeds. Since then, this model has been adopted by all other dog clubs around the world.\u00a0 The closed pedigree book ensures the consistency and purity of traits for the pure breed in question. However, this desirable uniformity of traits comes at a cost, as it also leads to genetic uniformity which can be problematic. See the section on inbreeding<\/a>.<\/p>\r\n\r\n

Recognized Purebred Dog Breeds<\/h3>\r\n

Today there are between 400 and 500 different purebred dog breeds recognized by numerous breeding clubs around the world.\u00a0 For example, the American Kennel Club (AKC) recognizes 189 different pure breeds, the Canadian Kennel Club (CKC) recognizes 175, and the Kennel Club of England (The Kennel Club), the first to be created, recognizes 210.\u00a0 These numbers are not static but can and do change over time.\u00a0 It is important to note that, for modern purebred dogs, the choice of parents for the next generation of puppies is made based on performance in competitions, in other words, on human decisions and artificial selection. \u00a0An animal that performs well in competitions is judged an animal that meets the standards of the breed in question, and will have its genetics, both good and bad, transmitted to the next generation.<\/p>\r\n

\u00a0<\/p>\r\n

\"\"<\/a> <\/p>\r\n\r\n

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Breeding Strategies<\/h3>\r\n

Several breeding strategies are available to the dog breeder, including:<\/p>\r\n

Inbreeding<\/strong> – involves breeding of animals that are members of the same family, with common ancestors on both paternal and maternal sides of the pedigree.\u00a0 This will maintain (fix) the desired phenotypes in the offspring but at the same time will reduce the genetic variation found within the offspring.\u00a0 Inbreeding will increase the coefficient of inbreeding<\/a> of the offspring compared to the parents.\u00a0 Another name for inbreeding is an incestuous breeding. <\/p>\r\n\r\n

Line breeding<\/strong>\u00a0– involves breeding of animals that are members of the same breed and show similar traits but come from different lines (pedigrees).\u00a0 Thus, there is no (or very little) common ancestry.\u00a0 This is a compromise between obtaining the desired traits for the breed while still maintaining an equilibrated genetic base within the offspring.\u00a0 The coefficient of inbreeding of the offspring will be maintained at about the same level as the parents. \u00a0Not all dog breeds have the sufficient numbers of animals to support line breeding.<\/p>\r\n\r\n

Outbreeding<\/strong> – involves the breeding of animals of the same or similar breeds, from completely different lines where traits are not necessarily similar.\u00a0 There are no ancestors in common.\u00a0 The desired physical traits are not necessarily maintained in the offspring.\u00a0 The genetic variation of the offspring is increased compared to that of the parents, thus reducing its inbreeding coefficient. <\/p>\r\n\r\n

Crossbreeding<\/strong>\u00a0– involves the breeding of animals of two different breeds; there are no ancestors in common.\u00a0 Neither the type of the paternal parent nor the type of the maternal parent is maintained in the offspring.\u00a0 The genetic variation of the offspring is increased compared to that of the parents, and its coefficient of inbreeding is reduced. <\/p>\r\n\r\n

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Pedigrees<\/h3>\r\n

\"\"<\/a>Pedigrees are the official record of the parentage and thus the ancestry of an animal.\u00a0 They are an integral part of the official record keeping required by a breed club to register new animals.\u00a0 Pedigrees are also a valuable resource for the genetics of an animal, whereby the genetic contribution of a particular ancestor can be estimated and the genetic relatedness of two individuals can be determined.\u00a0 As we will see, the pedigree is also used for determining inbreeding estimates for animals.<\/p>\r\n

Pedigrees are organized like the branches of a tree.\u00a0 In the standard format, the paternal contribution is presented above and the maternal contribution is presented below for the animal (offspring) in question.\u00a0 With each generation, the genetic contribution of a particular ancestor is divided by two.\u00a0 Thus, an animal (offspring) has 2 parents each of whom contributed 50% to the genetic constitution of their offspring and 4 grandparents each of whom contributed 25% to the genetic constitution of the offspring, and so on.\"\"<\/a><\/p>\r\n

Inbreeding<\/h3>\r\n

When two animals that share common ancestors are bred together, a condition of inbreeding exists in the offspring.\u00a0 This inbreeding has two consequences for the phenotype of the offspring:<\/p>\r\n

    \r\n
  1. Increased uniformity of \u201ctype\u201d<\/strong> (i.e. phenotype) within the offspring, with increased \u201cprepotency\u201d, i.e. the ability of parents to transmit or fix a phenotype in the next generation. This uniformity of type is desirable to breeders.<\/li>\r\n
  2. Inbreeding depression<\/strong>, which includes a reduction of vitality, reduced weight, reduced fertility, reduced rate of growth; increase rates of congenital anomalies, increased mortality, increased rates of recessive genetic diseases; a shortened life span.\u00a0 Inbreeding depression is cumulative: with increased inbreeding, there is an increase in inbreeding depression.<\/span><\/span><\/li>\r\n<\/ol>\r\n

    \"\"<\/a>At the level of the genome, inbreeding has the effect of increasing the percentage of homozygous genetic alleles (N\/N, M\/M<\/strong>) and reducing the percentage of heterozygous genetic alleles (M\/N<\/strong>, carriers).\u00a0 Mutations that are recessive will accumulate in the homozygous state, (M\/M<\/strong>), thus increasing the frequency of recessive genetic disease, which contributes to the deleterious effects of inbreeding depression. See Labgenvet’s page on Dog Genetics 3.0 Simple Genetic Diseases<\/a>.<\/p>\r\n

    Stated simply, Mother Nature does not like uniformity, neither in phenotypes nor in genotypes.\u00a0 She much prefers variations, diversity, differences.<\/p>\r\n

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    Our modern purebred dog breeds are pretty much by definition, inbred groups of animals.\u00a0 The limited number of foundation animals for a purebred breed, closed pedigree books for the breed and the tendency to use only a fraction of animals within a breed as parents for the next generation (champion dog effect, popular stud effect) all contribute to the reality that our purebred dog breeds represent inbred populations.<\/p>\r\n

    The Coefficient of Relation (a)\u00a0and the\u00a0Coefficient of Inbreeding\u00a0(COI)<\/h3>\r\n

    In 1921-22, Sewall Wright, an American mathematician and geneticist, defined two mathematical values based on a given genetic pedigree: the\u00a0Coefficient of Relation (a)<\/strong>\u00a0and the\u00a0Coefficient of Inbreeding<\/strong>\u00a0(COI<\/strong>, inbreeding coefficient or sometimes simply \u201cF<\/strong>\u201d).\u00a0 These two values are useful for the art and science of domestic animal breeding.\u00a0 Neither of these values represents specific DNA or genes of an animal.\u00a0 They are abstract values, calculated on the assumption that all of our genes follow simple mendelian genetics with dominant and recessive alleles (versions).\u00a0 This assumption is of course simplistic.\u00a0 In spite of this reality, the Coefficient of Relation and the Coefficient of Inbreeding have proven to be useful measures with practical applications for animal and plant breeders.\u00a0 They allow an estimation of the genetic relationship between two animals and also an estimation of the genetic variation (or lack thereof) found within the genome of a particular animal.\u00a0 With these measures, breeders can estimate the risks of having undesirable health effects (inbreeding depression) in future generations due to a lack of genetic variation caused by too much inbreeding.<\/p>\r\n

    \r\n

    The Coefficient of Relation (a)<\/strong> is an estimation of the quantity of DNA that is in common between two animals within a pedigree.\u00a0 The simplest formula representing the coefficient of relation is as follows:<\/p>\r\n

    \"\"<\/a><\/p>\r\n

    Where:<\/p>\r\n

    a\u00a0= the Coefficient of Relation between two animals.<\/p>\r\n

    \u00bd = the genetic contribution of a parent towards its offspring.<\/p>\r\n

    n\u00a0<\/em>= the number of pathways (number of generations) that separate two animals within a pedigree.\u00a0 Stated differently,\u00a0n<\/em>\u00a0is the number of meiosis (cell division of sex cells) separating two animals. In other words, the number of times productive sex occurred between the ancestors (or descendants) of the two animals in question.<\/p>\r\n

    \u2211 = the sum of the calculations for all possible pathways linking the two individuals.<\/p>\r\n<\/blockquote>\r\n

    This equation is derived from the fact that we (and our dogs) are diploid, and that we have received half of our DNA from our mother and the other half from our father.\u00a0 The DNA of our parents was divided in two (1\/2) within their germ cells, and then added together (1\/2 + 1\/2) during fertilization to generate the full double (diploid) genetic complement (100% or 1.0) needed to form us and make us function.\u00a0 If two animals are not genetically linked then their Coefficient of Relation is 0.\u00a0\u00a0 On the other hand, if two animals are linked within a pedigree, their Coefficient of Relation will be higher than 0 and can be calculated.<\/p>\r\n

    \r\n

    <\/a>The Coefficient of Inbreeding <\/strong>(COI<\/strong>, inbreeding coefficient, \u201cF<\/strong>\u201d) is an estimation of the loss of genetic variation for an individual animal, due to the fact of having a common ancestor on both the paternal side and the maternal side of its pedigree.\u00a0 The Coefficient of Inbreeding can be derived from the Coefficient of Relation by the following simple formula:<\/p>\r\n

    COI \u00a0= \u00a0(1\/2)\u00a0a \u00a0<\/em>= \u00a0(1\/2) <\/strong>n+1<\/sup><\/em><\/strong><\/p>\r\n

    A more comprehensive presentation of the Coefficient of Inbreeding formula is as follows:<\/p>\r\n

    \"\"<\/a><\/p>\r\n

    Where:<\/p>\r\n

    F\u00a0= the Coefficient of Inbreeding (COI) for the individual in question.<\/p>\r\n

    \u00bd = the genetic contribution of a parent towards its offspring.<\/p>\r\n

    n<\/em>\u00a0<\/em>= the number of pathways (number of generations) between a common ancestor and the individual in question.<\/p>\r\n

    +1 = an additional factor of (1\/2) is added to represent the anticipated loss of genetic diversity due to common ancestors on both maternal and paternal sides of the pedigree.<\/p>\r\n

    \u2211 = the sum of the calculations for each individual ancestor in common.<\/p>\r\n

    If the common ancestor has itself common ancestors, then the common ancestor will itself have a positive inbreeding coefficient value.\u00a0 The inbreeding coefficient for the animal in question is now multiplied by the following correction factor:<\/p>\r\n

    (1 + Fa)<\/strong><\/p>\r\n

    Where:<\/p>\r\n

    Fa = the Coefficient of Inbreeding for the ancestor in common.\u00a0<\/p>\r\n<\/blockquote>\r\n

    For intrepid souls, mathematical masochists, mad dogs and Englishmen, these formulas can get even more complex:\u00a0<\/p>\r\n

    http:\/\/www.genetic-genealogy.co.uk\/Toc115570144.html<\/a><\/u>\u00a0<\/p>\r\n

    http:\/\/www.genetic-genealogy.co.uk\/Toc115570148.html<\/a><\/u>.<\/p>\r\n

    Examples of Coefficients of Relation and Coefficient of Inbreeding<\/h3>\r\n

    Here are some examples of Coefficients of Relation (once again, the average amount of shared DNA) between two parents without common ancestors, as well as the Coefficient of Inbreeding (measurement of loss of genetic diversity) for their hypothetical offspring:<\/p>\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n
    Relationship<\/strong><\/td>\r\nCoefficient of Relation (a)<\/strong><\/td>\r\n\r\n

    Coefficient of Inbreeding (COI) <\/strong><\/p>\r\n

    of offspring<\/strong><\/p>\r\n<\/td>\r\n<\/tr>\r\n

    Parent – child<\/td>\r\n50%<\/td>\r\n25%<\/td>\r\n<\/tr>\r\n
    Brother – sister<\/td>\r\n50%<\/td>\r\n25%<\/td>\r\n<\/tr>\r\n
    Grandparent \u2013 grandchild<\/td>\r\n25%<\/td>\r\n12.5%<\/td>\r\n<\/tr>\r\n
    Uncle\/aunt \u2013 nephew\/niece<\/td>\r\n25%<\/td>\r\n12.5%<\/td>\r\n<\/tr>\r\n
    Half brother \u2013 half sister<\/td>\r\n25%<\/td>\r\n12.5%<\/td>\r\n<\/tr>\r\n
    Cousins<\/td>\r\n12.5%<\/td>\r\n6.25%<\/td>\r\n<\/tr>\r\n
    Half-cousins<\/td>\r\n6.25%<\/td>\r\n3.125%<\/td>\r\n<\/tr>\r\n
    Second cousins<\/td>\r\n3.13%<\/td>\r\n1.063%<\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\n

    For example, a child shares 50% of its genes with its parent, and the Coefficient of Relation (a) between the parent and child is 50%.\u00a0 The child has a Coefficient of Inbreeding of 0.\u00a0 However, the offspring resulting from an incestuous relationship between a parent and their child, or between a brother and sister, will have a Coefficient of Inbreeding of 25%.\u00a0 This means that, on average, there will be a 25% loss of genetic variation (loss of M\/N) and an equivalent 25% gain in genetic uniformity (gain in N\/N, M\/M) at the level of the offspring\u2019s DNA.\u00a0 Breeding of close relatives (parent\/child, brother\/sister) are now banned by certain progressive canine associations such as The Kennel Club (of England), but not by all kennel clubs.\u00a0 In terms of human laws, marriages between cousins are generally permitted even if children resulting from such marriages will have a Coefficient of Inbreeding of 6.25%.<\/p>\r\n

    The Kennel Club (of England) – average inbreeding coefficients<\/h3>\r\n

    The Kennel Club (www.thekennelclub.org.uk<\/a>) calculates the current average value for inbreeding coefficients (COI) for a given breed of dog.\u00a0 These values are based on the pedigrees of puppies from the United Kingdom registered by The Kennel Club for a given breed during the previous year.\u00a0<\/p>\r\n

    Based on The Kennel Club\u2019s calculations, here are some examples of average inbreeding coefficients based on pedigrees for several dog breeds in the United Kingdom, for 2019:<\/p>\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n
    Breed<\/strong><\/td>\r\nCOI (%)<\/strong><\/td>\r\nBreed<\/strong><\/td>\r\nCOI (%)<\/strong><\/td>\r\n<\/tr>\r\n
    Airedale Terrier<\/td>\r\n17.6<\/td>\r\nBrittany<\/td>\r\n5.7<\/td>\r\n<\/tr>\r\n
    Yorkshire Terrier<\/td>\r\n11.3<\/td>\r\nNewfoundland<\/td>\r\n5.0<\/td>\r\n<\/tr>\r\n
    English Cocker Spaniel<\/td>\r\n10.7<\/td>\r\nChesapeake Bay Retriever<\/td>\r\n3.4<\/td>\r\n<\/tr>\r\n
    Staffordshire Bull Terrier<\/td>\r\n9.5<\/td>\r\nShar Pei<\/td>\r\n3.0<\/td>\r\n<\/tr>\r\n
    Beagle<\/td>\r\n8.6<\/td>\r\nAustralien Shepherd<\/td>\r\n2.9<\/td>\r\n<\/tr>\r\n
    Labrador Retriever<\/td>\r\n6.6<\/td>\r\nGerman Shepherd<\/td>\r\n2.8<\/td>\r\n<\/tr>\r\n
    Dachshund, Wirehair<\/td>\r\n6.6<\/td>\r\nNova Scotia Duck Tolling (NSDTR)<\/td>\r\n1.6<\/td>\r\n<\/tr>\r\n
    Bullmastiff<\/td>\r\n5.9<\/td>\r\nEurasier<\/td>\r\n1.0<\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\n

     <\/p>\r\n

    For a more comprehensive list, you can consult Labgenvet’s page on:<\/p>\r\n

    Dog Genetics 4.2: Pedigree based Inbreeding Coefficients of dog breeds as calculated and provided by The Kennel Club, for 2019.<\/a><\/p>\r\n

    Inbreeding and the Loss of Genetic Diversity<\/h3>\r\n

    Once again, for a Coefficient of Inbreeding of 10%, this would mean that for genetic sites that are heterozygous (M\/N, carriers) in a common ancestor, there is a 10% chance that these sites will become homozygote (N\/N or M\/M) in the descendant.\u00a0 In other words, there is on average a 10% net loss of genetic diversity (or gain in genetic uniformity if you will) in the offspring due to matings involving inbreeding.\u00a0 A particular genetic site that has been converted from heterozygote (diversity) to homozygote (uniformity) in an offspring due to inbreeding is said to be\u00a0identical by descent<\/strong>\u00a0due to the common ancestor.<\/p>\r\n

    Pedigrees<\/h3>\r\n

    \"\"<\/a>How many generations of a pedigree should be considered when calculating the Coefficient of Inbreeding?\u00a0 The more generations that are available, the more reliable the calculation.\u00a0 Using a small number of generations tends to give coefficient values that are artificially low compared to values obtained when more generations are included.\u00a0 In practical terms, use all the pedigree information that is available.\u00a0 This could be as few as three generation or as many as all the generations in the pedigree going back to the founding animals for the breed.<\/p>\r\n

    Thanks to the goodwill of breeders and to the power of the internet, many dog pedigrees are available on web sites dedicated to this purpose.\u00a0 Here are several examples:<\/p>\r\n

    https:\/\/breedarchive.com\/home\/index<\/a><\/p>\r\n

    http:\/\/www.k9data.com\/<\/a><\/p>\r\n

    For a given animal, the known pedigree is presented, common ancestors are noted, and often inbreeding coefficients can be calculated for the known generations.\u00a0 A useful function for breeders is the ability to calculate and compare inbreeding coefficients for possible future breedings (\u201cvirtual<\/strong>\u00a0breeding<\/strong>\u201d function).<\/p>\r\n

    Using Inbreeding Coefficients<\/h3>\r\n

    \"\"<\/a>Inbreeding coefficients, used correctly, are a powerful tool for breeders when it is the time to choose the parents of the future generation of dogs. \u00a0In a general fashion, the inbreeding coefficient is an indication of the global state of genomic health of an animal.\u00a0 The genome is the sum total of all the genes that are necessary for the creation as well as the function of an animal.\u00a0 More specifically (as mentioned above), the inbreeding coefficient represents a numerical percentage, based on the analysis of a pedigree, that estimates the loss of genetic variation in an individual caused by the fact of having common ancestors on both the paternal and the maternal sides of the pedigree.\u00a0 \u00a0Having common ancestors on the two sides of the pedigree will result in a percentage of genetic sites that were heterozygous (M\/N) in the common ancestor to become homozygote (either N\/N or M\/M) in the descendant.\u00a0 This condition is known as being identical by descent<\/strong> due to the fact of having a common ancestor.<\/p>\r\n

    From the genetic perspective, a loss of genetic variability is undesirable as it can result in the condition of inbreeding depression<\/strong>.\u00a0 Inbreeding depression has been well documented for many animal and plant species.\u00a0 Also well documented is the effect of outbreeding or crossbreeding, which will increase the genetic variation in the genome of an animal and result in hybrid vigor<\/strong> (heterosis).\u00a0 Hybrid vigor is the genomic flip side of inbreeding depression.<\/p>\r\n

    \"\"<\/a>It is important to keep in mind that the inbreeding coefficient does not represent the genetic variation that will be found at a specific genetic site or gene, but rather is a global estimation of genetic variation for the genome of an animal.\u00a0 If there are no common ancestors between the paternal side and the maternal side of a pedigree, the offspring will have no loss of genetic variation compared to a standard population.\u00a0 The offspring will then have an inbreeding coefficient of 0.\u00a0 If there are common ancestors on both the paternal and the maternal side of the pedigree, there is now the potential of loss of genetic variation (genetic identity by descent), and the potential for inbreeding depression.\u00a0 The Coefficient of Inbreeding is now a positive number greater than 0, often expressed as a percent.\u00a0 It is estimated that for every 1% increase in the inbreeding coefficient there is a 1% reduction in whatever trait is being measured.\u00a0 In practical terms the inbreeding coefficient is most useful for estimating the effects of recent inbreeding.<\/p>\r\n

    It is not surprising that Mother Nature likes genetic variation as this is the long-term key to the survival and evolution of a species.\u00a0 Unfortunately for our domestic animals, breed standards favor phenotypic uniformity (breeding for type<\/strong>), and in order to achieve this uniformity, a certain level of inbreeding and reduced genetic variation is involved.<\/p>\r\n

    Interpretation of Inbreeding Coefficients<\/h3>\r\n

    \"\"<\/a>An elevated inbreeding coefficient for an animal indicates that the undesirable effects of inbreeding (i.e. inbreeding depression) will start to be evident.\u00a0 On the other hand, an elevated inbreeding coefficient will increase the chances that desirable traits associated with the breed in question will be fixed.\u00a0 Thus, the inbreeding coefficient can be viewed as a compromise.\u00a0 The deleterious effects associated with inbreeding start to be seen when the coefficient of inbreeding is higher than 5%, which is just below the value obtained for the offspring of a mating between two cousins (=6.25%).\u00a0<\/p>\r\n

    It is advised to maintain a coefficient of inbreeding that is below 10% which should allow a number of desired traits to be fixed without allowing the undesirable effects of inbreeding to become too pronounced.\u00a0 Incestuous crosses resulting in offspring with coefficients of inbreeding above 12.5% should not be performed; these include parent-offspring, brother-sister, grandparent-grandchild, half-brother-half-sister matings.\u00a0\u00a0 In practice it is recommended to choose crosses that will result in offspring that have reduced coefficients of inbreeding compared to the average of the breed in question.\u00a0 If a number of breeding possibilities are available that will reduce the average inbreeding coefficient in the offspring compared to the breed average, then ideally the breeding that will result in the lowest inbreeding coefficient while still maintaining the desired traits for the breed<\/em> is recommended.<\/p>\r\n

    [\/vc_column_text][\/vc_column][\/vc_row][vc_row el_class=”bloc_info”][vc_column][vc_column_text]<\/p>\r\n

    In general:<\/strong><\/p>\r\n

      \r\n
    1. Select a breeding pair that will reduce the coefficient of inbreeding in the offspring compared to the average of the breed<\/strong>.<\/strong><\/li>\r\n
    2. If possible, do not use an animal for breeding if it has common ancestors within its pedigree, at least not within the 3 to 4 most recent generations.<\/strong><\/li>\r\n
    3. Avoid incestuous breedings, with coefficients of inbreeding of 12.5% or greater.<\/strong><\/li>\r\n
    4. Try to keep inbreeding coefficients lower than 10%.<\/strong><\/li>\r\n
    5. Ideally, keep inbreeding coefficients lower than 5%.<\/strong><\/li>\r\n
    6. Think about sacrificing a bit of “type” (physical characteristics for the breed in question) in an individual animal in order to increase the genomic health of your breed.<\/strong><\/li>\r\n<\/ol>\r\n

      [\/vc_column_text][\/vc_column][\/vc_row][vc_row][vc_column][vc_column_text]Link to Labgenvet’s Inbreeding Calculator.<\/a><\/p>\r\n

      Link to Labgenvet’s page on Dog Genetics 4.1: Inbreeding Calculator, Detailed Instructions and Interpretation<\/a><\/p>\r\n

      \u00a9 2019 David W. Silversides[\/vc_column_text][\/vc_column][\/vc_row]<\/p><\/div>","protected":false},"excerpt":{"rendered":"

      [vc_row][vc_column][vc_column_text] Dog Genetics 4.0: Evolution, Breeds, Breeding Strategies and Inbreeding   The Evolution of Dogs The dog (Canis familiaris, or Canis lupus familiaris) is a multiparous carnivore.\u00a0 Its genome consists of 2.4 billion bases organized on 39 pairs of chromosomes, plus one mitochondrial chromosome. The dog holds the title of the first animal domesticated and…<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"_acf_changed":false,"footnotes":""},"class_list":["post-15350","page","type-page","status-publish","hentry","description-off"],"acf":[],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/labgenvet.ca\/en\/wp-json\/wp\/v2\/pages\/15350","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/labgenvet.ca\/en\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/labgenvet.ca\/en\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/labgenvet.ca\/en\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/labgenvet.ca\/en\/wp-json\/wp\/v2\/comments?post=15350"}],"version-history":[{"count":143,"href":"https:\/\/labgenvet.ca\/en\/wp-json\/wp\/v2\/pages\/15350\/revisions"}],"predecessor-version":[{"id":24193,"href":"https:\/\/labgenvet.ca\/en\/wp-json\/wp\/v2\/pages\/15350\/revisions\/24193"}],"wp:attachment":[{"href":"https:\/\/labgenvet.ca\/en\/wp-json\/wp\/v2\/media?parent=15350"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}