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inbreeding diversity pedigree linebreeding genes genetics dog crossbreeding outcrossing animal husbandry Fred Lanting

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INBREEDING AND DIVERSITY - PART 4

by Fred Lanting

Copyright January, 2009 -

Continued from PART 3

The first thing we do is add a column and a row to the table that we will fill in with coefficients of relationship between Z, the offspring of Emma and Y, and the rest of the dogs in the pedigree. We can also fill in the Z-Z cell because we already know the relationship between Y and Emma is 3/8, giving Z a coefficient of inbreeding of 3/16 (18.75%). The normal procedure is then followed to complete the table, which is presented below.

The shaded row and column contain coefficients of relationship between Z and the other dogs in the pedigree. We can clearly see that relationships between these animals are rising quickly because of the ties back to Emma in three out of four generations. Many breed societies have rules that dictate how frequently the same animal may appear in a pedigree, perhaps four times in six generations, and those rules are based on this idea. However, you can now see that the influence of such an individual depends quite a lot on just where in the pedigree the repeat appearances are. A more sensible rule might be that animals with a coefficient of inbreeding beyond a certain threshold will not be issued papers.

A second approach would be to restrict the average relationship to influential members of the breed. The American Jersey Cattle Club publishes what they call a coefficient of kinship (K) on their pedigrees. That number represents the average relationship between the pedigreed individual and a set of the most influential sires in the Jersey breed. A disadvantage of this approach, however, is that K cannot be computed using the tabular method or other simple technique, and can vary considerably depending on the definition of the “most influential” group.

Introducing Genetic Variation through Crossbreeding

Breeds small in numbers (such as the Shiloh Shepherd, certainly the Chinook and Klee Kai) are sometimes faced with the need to introduce genetic variation from an outside source to keep their population viable. This is typically done using crosses between the breed’s base (small gene pool) and another breed deemed to be suitable. The decision of what breed to outcross with can be based on anatomical conformation, behavior, or some other characteristic important to the base breed. A concern is often to limit the influence of the new breed to maintain an acceptable level of “purity”, or breed composition. An approach to calculating the outcome of matings between base and outcross animals will be presented and discussed.

Outcrossing may be used to take advantage of a phenomenon erroneously known as “hybrid vigor”, more properly heterosis.  The idea is that a cross between two populations that have each become relatively homozygous will produce offspring that are heterozygous at many loci.  Research has shown that such crosses are often much heartier, healthier and productive than either of the parental lines.  Heterosis is an effect dog breeders have known about and taken advantage of for many years. [Note: technically, a hybrid is a cross between two species, such as horse X jackass, or bison X cattle; crossbred dogs or dog-wolf matings do not produce true hybrids. But we should recognize that the word is used, and consider the context, even though a wolf is just another breed of dog.]

A tabular approach can be used to determine levels of breed composition.  By breed composition, we mean the percentage of base and outcross breeds in the improved population.  For example, if you were to cross populations of German Shepherds and Labradors, the composition of the resulting breed would be 50% GSD and 50% Labrador. Rules for acceptable matings are often based on distance between the outcross and current generation of individuals, and the tabular method to be presented can be used to determine if breed association rules are based on sound genetic ideas or breeder preferences.

We are going to use as the basis for this discussion a question posed to the author regarding breed composition and association rules. The situation is as follows: because of concerns about small population size, a breed association wishes to outcross for a single generation to bring in some new genetic variation. The outcross individuals will be used only for a single generation, and matings between composite (mixed) individuals will only be allowed if they are a certain distance apart in generations from the outcross. The rules as they currently stood stated that,  (A): 2, 3 and 4 may only mate with 5 and 6, and  (B): 5 and 6 may only mate with 2, 3, 4, 5, and 6.

Those numbers refer to distance, in generations, from the outcross event.  A ‘1’ would be the offspring of the limited-numbers breed and the introduced “outcross” breed.  We will use the pedigree in Figure 6 as the basis for our discussion.

Figure 6.  Seven Generations From an Outcrossing Event

1. “Outcross” represents the individual(s) of another breed
2.  “Pure” represents a purebred individual of the limited-numbers breed. Each of the “Pure” dogs above is a different individual.

(Read the above chart as: “Outcross” bred to the first “Pure” gave us #1;  #1 bred to another “Pure” gave us # 2, etc.)

We are going to use a table of eight generations (“Outcross” through 7) to show the breed composition of a mating between any two individuals an arbitrary number of generations from the outcross event.  Using the rules for computing a table of relationships presented earlier, we end up with the following table:

Continued in PART 5

General info on The Sieger Show Experience with tour guide Fred Lanting 

The  SV Bundessieger-Zuchtschau (BSZS or Sieger Show) in Germany is generally held in the last week of August or first week in September at a different location each year, depending on stadiums available. (The cost of stadium for this one-weekend event, and the competition with soccer/football events that sign contracts for many per year, determine the choice.) For the past 20 years or so, I have offered my non-profit 6-7-day guided tour of the show and sightseeing, including visits to kennels and training clubs. Get an SV judge's perspective of the bloodlines and procedures, along with experienced introductions to Germany's culture and beauty. My groups come from all parts of the globe, so even just the companionship is like a world-travel experience. We usually arrive on the Wednesday or Thursday before the show, and return the following Wednesday.

Looking for a great dog-related experience combined with seeing a different part of the world? Whatever your breed or activity in dogs, the annual Lanting guided show-and-sightseeing tour could be the experience of a lifetime. Read my annual “Impressions” articles on various websites for an idea of what we've seen in recent years. Tours centered on other countries’ Sieger Shows, the BSP, and world Schutzhund trials are also available if enough people sign up.    

None of "my people" have ever been sorry, and all have wished they had done it earlier! You will see the best of the breed, meet important GSD people, sometimes see another country or two, and have the over-all greatest dog show experience of your life. I also include, if you decide to join us, a variety of travel tips. I offer an SV conformation judge's perspective of the show (I also have AKC, UKC, and foreign judging experience). One year, when a travel-agency tour leader again deserted his group, they came to where my group was sitting and asked me questions. References available from previous tour participants. Testimonials are numerous. I hope you will join us and recommend this tour to your friends and acquaintances. As a judge with much experience in Schutzhund training and competition, and being very familiar with Western Europe, I am able to give the best tour possible. People going it on their own cannot see the important parts of the country (sometimes we tour adjacent countries, too), and paying for your rental car is more than chipping in to pay for the van and my expenses. Read my "Impressions" on various websites for an idea of what we've seen in recent years.

There will be 3 long days of the big show, and about 3 to 4 days of sightseeing and visits. Please let me know as soon as you can, with a $400 (US) deposit, so I can start putting my notification list together and finalize (hold) hotel reservations for you. There is a lot of work involved in putting together such a tour! I will make the hotel plans based on your deposits, & arrange the visits and van(s). Easy, fun, educational and, for most --- the unique trip of a lifetime. You will not be any younger next year, and if you don't make the decision to get out there and smell the roses NOW, while you think of it, you're more likely than not to lose the opportunity and desire.  Join the group! Tell others about it, too. Fred 

Contact me at  Mr.GSD[at]netscape.com and tell your friends and Internet contacts.
Postal mail: 3565 Parches Cove, Union Grove, AL  35175-8422 USA

Editor’s Note:  A well-respected and frequent GSD specialty and all-breed judge for many clubs around the world, with KC and other-country credentials, Mr. Lanting since 1966 has lectured on Gait-and-Structure, Canine Orthopedic Disorders, and other topics, and has judged in about 30 countries, including the prestigious FCI Asian Shows hosted by Japan Kennel Club and the KC of India, the Scottish Kennel Club, and many National Specialties in the USA and elsewhere. He has been described by a former OFA director as the world’s leading non-veterinarian authority on hip dysplasia. A dog breeder since 1945, a GSD owner since 1947, and a show judge since 1979, he has lectured at numerous veterinary schools in the USA and abroad. He is the author of “must read” books for the dog owner (see below for ordering info).  Curriculum Vitae available upon request.

Announcing the new “Canine HD and Other Orthopedics Disorders” book: The expanded revision is a comprehensive (nearly 600-page), amply illustrated, annotated, monumental work that is suitable as a coffee-table book, a reference work for breeders and veterinarians, and a study adjunct for veterinary students. It is equally valuable for the owner of any breed. It covers every aspect of HD and other orthopedic, bone, or spinal disorders, and includes genetics, diagnostic methods, treatment options, and the role of environment. Your autographed copy will be mailed from the USA as soon as the appropriate amount is received and is processed. Pricing: US $68, plus $5 postage in the U.S., or ask about mail overseas. Combine orders with “The Total German Shepherd Dog” by the same author ($50 plus postage). 17 of the 20 chapters are suitable for owners of any breed.