Tag Archives: genetic

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!

References

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

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Did Our Gene Pool Shrink (Again) in 2015?

In 2015 the number of AKC registered Gordon Setters continued it’s 20 year drop, down by another sixty dogs. Is there any end in sight to this trend, and are we seeing the first signs of extinction for some purebreds, including our own breed? In the last 20 years the Gordon Setter population has dropped by 71%. What is the impact to a breed like ours when 71% of their population is no longer available for breeding?

In the U.K., The Kennel Club considers the Gordon Setter as a “vulnerable” breed at only 234 registrations in 2015. I’m wondering how we should label the Gordon here in the states, considering that the population of the U.S.,  319 million, is nearly five times that of the U.K. at 64 million, but the U.S. Gordon Setter at 381 new registrations is only about one and a half times the 234 registrations in the U.K., a significantly smaller per capita number.

Could this mean that the breed is in an even more precarious and vulnerable position in the U.S.?

With this alarming decline in the breed’s population, if you’re breeding Gordon Setters there are a few things to consider as you go about planning new litters, and one of those considerations includes the need to develop a good understanding the of the gene pool and how your choices will impact preservation of the breed.

Your next litter is like a big fish in a small pond. As there fewer and fewer Gordon Setters whelped each year, the overall number of Gordon Setters available for breeding is dropping to an all time low, so litters that are born now will have a bigger impact on the future and preservation of the breed than the many litters that were born 20 years ago. Is it possible that we are losing genetic diversity in our breed population due to the decline in the overall number of new litters produced, and that our gene pool might also be shrinking? Unfortunately that answer may be Yes.

As breeders then, we need to ensure we have a basic understanding of genetic concepts and what it means to maintain genetic diversity. As our pool of fertile dogs continues to decline in number, the chance of finding unrelated genetically diverse dogs has fallen dramatically, which becomes especially relevant if we later find we need those dogs to help resolve a health issue from a newly recognized gene mutation.

Just as we pay attention to the need for health clearances when preparing for a litter, so too must we pay similar attention to understanding and analyzing the pedigrees of the resulting litter. Now is the time when we need to embrace the concept of preserving  offspring from the bloodlines of many various kennels and engage in preserving semen from healthy dogs of good quality, preserving many dogs of good quality from both show and field, not only those who are our top winners. Should we be doing more and more blending of the typical show and the field lines, or importing semen or dogs from other countries? These tactics and many more, now more than ever before need our attention, as breeders work to preserve the best qualities of our gorgeous breed, along with the diversity in our gene pool needed to safely continue the Gordon Setter in a healthy state.

With all that said, the following is an excellent article to get you started from The Institute of Canine Biology. It is a basic discussion about the gene pool. Today’s “Required Reading” for every Gordon Setter breeder I do believe!

What’s in the Gene Pool?

The founding of the breed – the Gene Pool

pool.jpgLet’s pretend these 11 dogs are the “founders” of your breed – they are the first dogs entered into the studbook.  All subsequent members of the breed are descended from these dogs only.  The breed has a closed gene pool.

All of the genetic variability that will ever exist in your new breed is present in these dogs.  Mutations probably won’t add new, useful genetic variation because most mutations are detrimental.  If the mutated gene is dominant and detrimental, it will likely be weeded out very quickly.  If the mutation is recessive, it is not expressed unless an animal is homozygous for the allele by inheriting a copy from each of its parents.  In the heterozygote condition, a mutated recessive allele can lurk in the genome for generations without ever causing a problem.  So, unless additional “founders” are added to the population at a later date, all of the genes you will ever have to work with in your breeding program are present in these dogs.

In each of these dogs there are at least a few (and perhaps many) recessive genes that could cause genetic disorders.  But these disorders will only expressed if a dog is homozygous for the disease allele – it must have TWO copies, one from each parent.  As long as the disease genes are rare in the population, very few animals will ever display the illness.

Can the gene pool get bigger? (No!)

Okay, starting with your 11 founder dogs, let’s let them reproduce.  To keep it simple, we will let them produce only identical copies of themselves – clones.

Now we have 27 dogs, all of which are exact copies of one of the founders.  What has happened to the size of the gene pool?

Nothing.pool1

You now have more dogs, and you now have more copies of the genes found in the dogs that had more offspring, like that busy gray dog with the red tongue.  So, the frequency of particular alleles is different in this population than in the founders, but the number of different alleles in the population is exactly the same.  (We’re ignoring the possibility of a mutation for now.)

What if the dogs reproduce normally instead of producing clones?  In sexual reproduction, each puppy receives one set of genes from each parent.  And, each puppy receives a different mix of parental genes, so each one is a bit different.  Also, each parent dog has a different number of offspring and might mate multiple times with different dogs.  So the frequency of the various alleles in the population could be very different in this new population than in the founders.

But again, even though there are now more dogs in the population, the gene pool does not get bigger.

In fact, it doesn’t matter how large this breed gets – it might someday grow to thousands of dogs – but as long as the stud book is closed, the gene pool will never be larger than it was when the breed is founded.

Can the gene pool get smaller?  (Yes!)

poo12The gene pool of a closed breed can never get bigger.  But it can get smaller.

What if dogs with black ears were less fertile, or had higher puppy mortality, or had some other biological problem?  The frequency in the population of the genes causing the black ears would be reduced by natural selection – black-eared dogs would contribute fewer copies of their genes to the next generation. Eventually, by genetic drift (chance) or natural selection, the genes in black-eared dogs would become rarer and rarer, and might eventually be eliminated from the population entirely.

What if breeders didn’t like black ears, so all the puppies with black ears were spayed or neutered and sent to pet homes?  Those alleles will become less frequent in the population, and they might be eliminated completely because of artificial selection courtesy of the breeder.

The gene pool gets smaller when genes are completely eliminated from the population.  It is unlikely that a gene will be restored by chance mutation, and the only other way it can be restored is if an animal is introduced into the breeding population that carries that gene and who reproduces successfully.

In purebred dogs, when the stud book is closed, no new alleles can be introduced into the breed.  The loss of an allele is permanent and reduces the heterozygosity in the genome for that gene.

http://www.instituteofcaninebiology.org/whats-in-the-gene-pool.html

Sally Gift, Mesa AZ

 

 

 

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Q & A From the Breeding Survey – Kinked Tails causes of?

Some of our readers, who have completed our Breeding Survey, have posted questions which we will research and hope to answer. Thank you to those who have already completed the survey and shared questions with us!

One of the questions posted was:

“One puppy in each litter born with kinked tail; I would like to find out, if possible, if this is due to the womb environment or to a genetic factor.”

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Puppy born with a kinked tail. Sometimes these involve only the very tip of the tail but can be even more obvious as shown in this photo.

An article we published in January answers that question and we believe you will find it helpful! Simply click on the following title to be taken to The Kinked Tail – More Than it Appears. 

Readers did you know you can search for information on Gordon Setter Expert by clicking the little magnifying glass on the top left hand bar of the site opening a search text field. Or you can search for articles by their general topic by clicking on any of the categories found on the sidebar columns. Scroll down the page once your category opens to find all articles currently published on that topic. Categories include topics like Breeding, Care (feeding, grooming etc.) Dog shows, Performance events, etc.

GORDON BREEDERS WE NEED YOU:  We have created a very quick online survey for Gordon Setter breeders that will help us learn what, if any, issues you may have encountered in producing quality litters. We are preparing for an upcoming seminar on reproduction and need your input in order to prepare topics that would be most relevant to you. Please take one minute to link to the survey only if you own a bitch or bitches you have bred or attempted to breed in the past 5 years. The survey is completely anonymous.

This link when clicked will take you directly to the survey’s 8 easy questions.

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