Tag Archives: dog genetics

Let’s Talk Linebreeding

“One of the most bandied about terms among breeders today seems to be linebreeding. Despite it’s widespread use, however, linebreeding is frequently misunderstood and miscommunicated; in fact, it is not altogether uncommon for an outcrossed pedigree to be mistakenly viewed as linebreeding by the novice. The present discussion defines linebreeding and how we can more accurately define our linebred litters.”

From – “Let’s Talk Linebreeding” written by Claudia Waller Orlandi, Ph.D. published in ‘Tally Ho’ the Basset Club of America Newsletter (July-August ’97). The online article may be found by clicking here.

(While this article was written with the Basset Hound breeder in mind, one can change the name to  Gordon Setter, or any breed for that matter, as the material is “one size fits all” when it comes to the topic of breeding.)

Linebreeding and Inbreeding: A Family Affair

Inbreeding and Linebreeding involve the mating of animals within the same family. Breeding relatives is used to cement traits, the goal being to make the offspring homozygous (pure) for desirable characteristics. Homozygous dogs tend to be prepotent and produce offspring that look like themselves (Walkowicz & Wilcox 1994)

Willis (1989) defines Inbreeding as the mating of animals “more closely related to one another than the average relationship within the breed.” Inbred pairings would include brother/sister (the closest form) father/daughter, mother/son, and half-brother/half-sister.  Linebreeding involves breeding relatives other than the individual parents or brother and sisters. Typical linebred matings are grandfather/granddaughter, grandmother/grandson, grandson/granddaughter, great-grandmother/great-grandson, uncle/niece, aunt/nephew and cousin crosses. Linebreeding is a less intense form of inbreeding. Because of their focus on a dog’s potential genetic contribution, inbreeding and line breeding are termed genetic breeding systems.

figure-1-genetic-breeding-systems Definition:  For a dog to be linebred there must be an ancestor in the pedigree that is common to both the sire and the dam.  Figure 2 illustrates this concept. Kelly is linebred because the dog, Brahms, appears twice in the sire’s side and once in the dam’s side of the pedigree.figure-2-linebreedingCommon Misconception:  A pedigree may show either the sire and/or the dam to be linebred but no ancestor common to both the sire and dam. This is outcrossing, not linebreeding (see figure 3).  Similarly, because the same kennel prefixes (Windy, Hill, Castle) are common to both the sire’s and dam’s ancestors, the newcomer may mistakenly view the pedigree as linebreeding.figure-3-outcrossingWhere to draw the “Line”?

Breeders do not always agree on what constitutes linebreeding, with some feeling that common ancestors within the first five or six generations is linebreeding. Willis (1989) indicates that the farther back linebreeding is in a pedigree the less intensive it will be, pointing out that a dog appearing 12 times (out of a possible 32) in the 6th generation of a pedigree would have a Coefficient of Inbreeding (CI) of only 1.8% (by comparison, a sire to a granddaughter cross has a CI of 12.5%). The CI tell us the proportion of genes for which the inbred ancestor is likely to be homozygous, that is carrying the same genes from each parent. (Remember that homozygous animals have a higher potential for reproducing themselves.) In Willis’s (1992) view, a common ancestor farther back than the 2nd or 3rd generation will have little influence on the litter. Linebreeding beyond the fourth generation has even less genetic impact.

How much bang will we get for our buck (or Basset!)

Several modern writers (Walkowitz & Wilcox 1994; Willis 1992, 1989; Onstott 1962) view linebreeding and inbreeding as essentially the same  and differing only in degree of intensity. Whether one considers inbreeding and linebreeding to be the same or feels they are two distinct breeding systems, quantifying the degree to which an animal is linebred (or inbred) provides important information regarding its potential genetic contribution. As Willis (1989) states: “When describing inbreeding [or linebreeding] breeders often say their dog is inbred or linebred without further qualification. This is a very inadequate description. We need to know which dog the animal is inbred [linebred] to and the degree of inbreeding [linebreeding].” Put another way, how much “bang” will we get from our linebreeding?

Describing your Basset’s linebred pedigree: reading, writing and a little arithmetic!

Willis (1992) suggests that a concise yet meaningful way to express the extent of linebreeding (inbreeding) is to number the generations of the animal in question. The common ancestor(s) is assigned the generation number as he/she appears in the pedigree. The parents are the first generation (1), the grandparents are the second (2), great grandparents are the third (3), great-great-grandparents are the fourth (4) and so on.

As previously stated, Kelly’s pedigree (Figure 2) is an example of  linebreeding, with Brahms appearing on both the sire’s and dam’s side. On the sire’s side Brahms appears twice in the third generation (3). We can write this as 3.3. On the dam’s side, Brahms appears once in the second generation (2) and this is written simply as 2. Willis has suggested the following written and verbal formats for expressing the extent of line breeding in a pedigree:

Written Format

We would write: “Kelly is linebred on Brahms 3.3/2”

Verbal Format

We would say: “Kelly is linebred on  Brahms three, three TO two.”

In the Written Format notice we separate the sire’s and dam’s side of the pedigree by using a slash mark (think of a pencil making a slash mark); in the Verbal Format the word “TO” is used to separate the sire’s and dam’s side (think of talking “to” someone). This verbal and written format tells us the dog on which Kelly is linebred and the extent of the linebreeding. Smaller numbers indicate that a dog is more closely linebred; larger numbers of 4 and above (Willis 1989) indicate a lesser extent.

Linebreeding and pedigrees: a final caveat

Linebreeding and inbreeding are essentially the same, differing only in the degree of intensity. (In Willis’s view, the common ancestors beyond the 2nd and 3rd generations will not greatly influence the resulting litter.) We have described the ease with which an animal’s extent of linebreeding may be expressed by means of written and verbal models. Perhaps this format will be “adopted” by those Basset Hound breeders whose interest lies in linebreeding. In addition to facilitating the description of a linebred pedigree over the phone, it certainly provides important information regarding the potential outcome of a breeding. In this regard, two things bear repeating: (1) linebreeding (and inbreeding) are only as viable as a breeder’s knowledge of basic genetics (a topic which will be addressed in future columns) and (2) a linebred pedigree is only as valuable as a person’s ability to determine the virtues and faults of the dogs it contains. When we add the final ingredient of rigorous selection hopefully we are on the way to producing better Basset Hounds!


Onstott, K. 1980. The New Art of Breeding Better Dogs. Howell, New York.

Walkowicz, C. and Wilcox, B. 1994 Successful Dog Breeding. Howell, New York.

Will, M.B. 1968 A simple method for calculating Wright’s coefficient of inbreeding. Rev. Cubana Cienc.Agric. (Eng.Ed.) 2: 171-4

Willis, M.B. 1989 Genetics of the Dog. Howell, New York

Willis, M.B. 1992. Practical Genetics for Dog Breeders. Howell, New York

For more articles about breeding by Claudia follow the link below.

These articles were written by Claudia Waller Orlandi, Ph.D. All have been published in ‘Tally Ho’, the official newsletter of the Basset Hound Club of America

Thank you to Barbara Manson, WI for sharing this link with us.

Sally Gift, Mesa AZ

Photography by Susan Roy Nelson





Population Analysis of the Gordon Setter – Genetic status of purebred dogs in the UK

Many thanks to Jerry Nelson for sharing these links with us on our Facebook group Gordon Setters Students and Mentors. They are directly related to the genetic consequences that can arise from the decline in the Gordon Setter population here in the U.S., and though we do not have a similar study/review underway in the U.S. (that I am aware of – remember how  I said we are behind the eight ball on this issue?) we can certainly use these publications to gain an understanding of what’s at stake and the importance of the issue and our response to it..  My hat is off to the UK for this valuable information. Thank You!

To read the very important “The Kennel Club” report ” Population analysis of the Gordon Setter Breed published September 2015 click the bold title.

Photo of Mista by Susan Roy Nelson

Sally Gift, Mesa AZ

Genetic status of purebred dogs in the UK – The Institute of Canine Biology.

By Carol Beuchat PhD

Just published today in Canine Genetics and Epidemiology is a study of the population statistics and genetic diversity of all 215 breeds registered by the Kennel Club, using data from the pedigree database from 1980-2014. The paper is a welcome addition to the literature, updating and eclipsing the earlier (and epic at the time) study by Calboli et al in 2008.

If you’ve been wondering if you should take a course in population genetics, this paper will convince you. (Check out the courses that ICB offers here.) The health of the dogs we breed depends fundamentally on the quality of the gene pool, and assessments of the genetic health of the gene pool are necessarily based on population-wide analyses. So there is much here about effective population size (Ne), which is determined by the rate of change in the average level of inbreeding in the population.

At the core of the paper are data for inbreeding over the years since 1980. Unfortunately, the data for individual breeds are not in the paper, or even in the supplementary documents available from the publisher (where they would be available in perpetuity), but instead are available as individual pdf documents on the Kennel Club website. If the address to that web page should ever change (and surely it will), the link published in the manuscript will be useless. So, download your favorite breed now, just to be safe.

Summarizing their findings about inbreeding, they say:

“The trend over all breeds was for the rate of inbreeding to be highest in the 1980s and 1990s, tending to decline after 2000…to sustainable levels, with some modest restoration of genetic diversity in some cases.”

While there are breeds in which inbreeding does stabilize (e.g., the Labrador Retriever; figure on the right), it is certainly not the case that this is a general pattern across all breeds.


Below are some examples of breeds in which inbreeding doesn’t stabilize after 2000, but increases continuously over the period of the study. Perhaps these are breeds that didn’t benefit from a surge in imports after 2000 (wish we could see the data for imports), but there is no evidence that breeders have been adjusting breeding strategies to reduce the level of inbreeding. If that was happening, it would be evident in the distance between the observed and expected inbreeding lines in these graphs. The expected level of inbreeding assumes that breeding is random; the higher observed level indicates that the animals being bred together that are more closely related than the population average. This also indicates the potential magnitude of the reduction in inbreeding that could be achieved by a change in breeding strategy.

Average inbreeding coefficient over 1980-2014
Upper: English Cocker (left), English Springer (right)
Lower: Akita (left) , Bull Terrier (right)


English Cocker


English Springer




Bull Terrier

As I noted above, the effective population size (Ne) is determined by the rate of inbreeding in the population. The rule of thumb used by conservation biologists as the minimum Ne necessary to maintain a sustainably breeding population has risen over the last few years from 50 unrelated, randomly breeding animals to 100, and even more recently 500, as biologists reassess the realities of both in situ and captive animal management (you can read about the latest argument over revision here). That aside, it is useful to look at some of the data on Ne from the present study.

Below I have graphed the data for Ne (from the Supplementary documents) for those breeds in which there were more than 50 registrations per year; that is, the more populous breeds. I have superimposed lines at Ne = 50 (red), Ne = 100 (yellow), and Ne = 500 (green), to correspond with the various rules of thumb under debate.

Download a larger version of this figure:

Ne by breed.png

Download File

If we wanted to conservatively go with the minimum Ne of 500, only 2 breeds would make the grade, and only about half of the breeds with registrations higher than 50/year would make the Ne = 100 cutoff. There are a good number of breeds for which Ne is <50 on this graph, and I haven’t looked at it yet but I would wager that the majority of breeds with fewer than 50 registrations per year will be below the red line as well. (If there were 50 dogs in the population, half male and half female, and all animals bred, the Ne would be 50. Breeds with fewer than 50 registrations per year would be cutting it mighty close.)
There is much more that could have been done with the data available to the authors than they presented in the paper and supplements. Just for fun, I have pulled the data for Labrador Retrievers from the paper and supplements and (quickly) put together some graphs that might be useful for breeders. (Similar analyses can be done for the other breeds on request.)
For instance, below is a graph of the fraction of puppies produced each year by top-ranking sires. You can see that about 30% of the pups born yearly were produced by only the top 5% of sires.
The impact of top-ranked popular sires is even more obvious in this figure of the maximum number of pups produced by a single sire in a year compared to the population average. Note that the y axis is logged, otherwise the data for the averages would all be to low to see.

(You can see more of the analyses of the Labrador data here.)

I would have to say that, after a few hours of fiddling with the available data, the paper’s summary is rosier than the actual picture. The statement that levels of inbreeding are looking much better since 2000 is quite misleading – it could simply be an artifact of the importation of unrelated dogs, and there are plenty of breeds in which the rate of inbreeding has stayed on the same trajectory for decades and could very well continue. The number of breeds with effective population sizes well into the danger zone should be a heads up for breeders, especially in those breeds that could increase Ne with the simple strategy of breeding a larger fraction of available dogs and balancing the ratio of males to females (as I discuss here).

The caveat here is that these data are for an artificial population – the dogs registered with The Kennel Club. Before 2000, it was effectively a closed population, and since then has the addition of imports with only 3 generations of pedigree information, which makes them appear in analyses like this to be new, unrelated founders. At least The Kennel Club should be congratulated for including geneticists on their staff who have access to the pedigree data and the expertise necessary for these analyses. What a pity that the AKC does not do the same.

You can read The Kennel Club’s press release about the study here.

Why all the fuss about inbreeding?

I’m sharing another great article from the Institute of Canine Biology with you today on breeding and genetics written by Carol Beuchat PhD.  This blog and Carol’s writings offer a wealth of information for the serious dog breeder and I’m going to be

Photo by Laurie Ward
Photo by Laurie Ward

recommending quite a bit of reading from this site for just that reason.

In this article Carol covers the topic of genetic disorders and the choices breeders face when planning a mating. She says “Breeders know that they can use inbreeding to concentrate the genes for the traits they prefer and to increase the predictability of a breeding by reducing variation in the offspring. But breeders have no way to increase the good genes but not the bad ones through inbreeding. (There are ways this can be done, but not using inbreeding.)”

As breeders we simply must take time to learn and understand genetics.  “You will hear people say that their lines are “healthy”, or that a particular problem is “not in my lines” This is a quote from Carol’s blog that I’ve heard oh, so very often, from many, many breeders over the years. Before you assume that you are safe to use statements like this as fact, read this article. It will indeed help you to more fully understand what lies beneath the surface.

Click the link that follows to be whisked away to the land of Genetics! Why all the fuss about inbreeding? (Or “Why are there so many genetic disorders in dogs?”) 

Sally Gift, Mesa AZ

Photo by Laurie Ward
Photo by Laurie Ward