Chapter 17 - A Summary Of Color Breeding, Heritable Diseases And Defects, And A Final Word On Theory And Practice

We will attempt in this chapter to summarize the latest findings from genetic researches on the subjects of color breeding and heritable diseases and defects. After that, we will close with a few words of caution for the novice breeder who wishes to use genetic principles in his efforts to improve the breed or strain of his choice.

A. Color Breeding.

The genetics of the transmission of coat color is, except for a few colors, extremely complex and, consequently, little understood. This field of knowledge is not one being investigated by scores of researchers; there is no agreement among either breeders or exhibitors as to a specific terminology of the multitude of obtainable colors, and there is a marked unwillingness, though understandable, on the part of breeders to crossbreed in order to ascertain specific color transmissions. In fact, the very idea of crossbreeding may cause a "pedigree purist" to fall into a state of shock.

There is little doubt that the simplest and easiest coat color to breed is one which depends upon a single recessive gene, e.g., chocolate or blue. The colors which are apparently dominant but which prove to be heterozygous mixtures are the ones which cause the greatest confusion. Black or sable, resulting from incomplete dominants or from gene interaction, are much more difficult to establish as true breeding strains.

Even though the possible combinations of coat color factors are astronomical, most breeds are homozygous for a number of factors and usually have only two or three alleles of the others. Genetic prediction is, therefore, vastly simplified.

Blue to blue will yield a clear majority of blue. However, you can get any other color, except black or merle.

Sable to sable gives a majority of sable with a fair number of black-and-tans.

Liver to liver produces a full majority of liver though it is possible for any other color to show, except blue, merle, or black.

Black to black will throw a majority of black, but any other color, except merle, may appear.

Yellow to yellow usually yields only yellows or yellow and white. Certain breeds of yellow may produce recessive cream whites.

Yellow to sable will get all black puppies unless one of the parents is heterozygous sable and yellow. (From a purely theoretical viewpoint, liver, blue, or parti-color could sometimes occur.)

Merle to merle yields 50% of the progeny merle, 25% black, and 25% white. The whites will be both deaf and blind.

Brindle to brindle gets mostly brindles with a minority of fawns.

Agouti to agouti will show mostly agouti, though sable and bicolor may also be thrown, but never plain black.

Liver to yellow will produce a majority of black, though you may get some yellows with liver or black noses, or even a few livers.

Blue to liver yields overwhelmingly black, though if either parent has the blue or liver in pure recessive, "apricot" may result.

Black to agouti will show mainly black, though any other color of the agouti series may appear.

It should be noted that any of the above colors may also yield an occasional white or parti-white. Within a given breed white bred to white ordinarily gives only white. (Between breeds white to white may yield parti-colors.)

In closing this summary, we are in agreement with Marca Burns (1952) who writes, ". . . breeders could help scientists (and themselves!) by adopting a uniform terminology for describing coat colors. It would be most valuable if an atlas of coat colors could be published, using color photographs and naming the color in a manner agreed on by interested bodies. . . . Breeders could then refer to this atlas for the correct color-description when registering their dogs."

B. Heritable diseases and defects.

In considering heritable diseases and defects, the statements which follow should not be regarded as absolute and final. Research in this area has been scanty and all too frequently the conclusions reached are tentative. The data, however, represent the best efforts to date and, with a note of caution, may be accepted at genetic face value.

A Partial List of Heritable Defects and Diseases

Abnormal larynx                       Recessive in Skye Terriers.
Anterior pituitary                       Incompletely dominant to normal.
dysfunction
Asthma                                     Not known.
Cataract                                   Mendelian dominant in Alsatians; associ-
                                                ated with retinal atrophy in Irish Setters.
Cryptorchidism                         Irregular; common in dwarf and short-
                                                headed breeds.
Deafness
Distemper susceptibility
Eczema proneness Epilepsy
Haemophilia Hairlessness
Hernia, umbilical Hydrocephalus
Kidney stones, predisposition to
Microphthalmia
Oestrual weakness
Overshot jaw Retinal atrophy Shyness, extreme Spinal inflammations
Tail, absent or short
Tetany
Trembling
 
Recessive. (At one time common in white Bull Terriers and was traced to a widely used stud dog that passed on a recessive gene to his numerous progeny.) White Collies from the merle-merle cross are nearly always deaf, and partially or totally blind. The same condition also occurs in Harlequin Great Danes. Albinotic Pekingese also show a high frequency of deafness.

Not known definitely, though appears to be partially recessive in Bloodhounds, Basset Hounds and Bull Terriers.

Seemingly a periodic dominant in Pointers. Not known. Sex-linked recessive.

A dominant that seems to be lethal in homozygotes.

Multiple recessive genes.

Several recessive genes are involved.
Recessive in Dalmatians.

Appears in homozygous merles and harlequins.

Partially dominant.

A Mendelian recessive in Dachshunds. Mendelian recessive gene. Dominant or partially dominant.

Toy Spaniel and Bull types especially susceptible, though the transmission is not clear.

Irregular; in some instances dominant or lethal in homozygotes.

Irregular, may be due to a recessive gene in Scottish Terriers.

Irregular in Airedales with the precise transmission not clear.

C. Theory and Practice

For the following paragraphs we are much indebted to Marca Burns whose informative monograph, The Genetics of the Dog, yielded these highly desirable conclusions.

"If at any time it was possible to assess the merits of every living individual in a breed, giving a score number to each dog or bitch according to its quality, it would be found that there was a range from bad to excellent, and if the scores were plotted as a graph, the result would probably approximate to a 'normal curve.' (See page 241.) The merit of animals produced by any dog breeder could be plotted similarly, and the aim should be to produce a strain whose merit-curve lies above (further to the right, page 241) the curve for the breed as a whole. However, if success in competition is the aim, the curve to be considered for comparison is not that of the breed as a whole, but that of other competitors, and it is this level of merit which the successful strain must exceed. If the merits of two breeding animals place them both near one extreme of the curve— whether both are exceptionally good or exceptionally bad— their progeny will tend to be nearer to the average of the breed than the parents are, although the range of the litter will be towards the parents' end of the curve. If one parent is exceptionally good and the other bad, the tendency is for the range of merit of the litter to be similar to that of the breed or strain as a whole. A very mediocre bitch thus tends to produce some puppies better than herself even if her mate is equally mediocre, and if she is mated to a champion stud dog, not all the credit for the improved merit of the litter as compared to their dam is really due to the dog. Similarly, when two champions are mated together, they cannot be expected to produce a litter of puppies all as good as themselves, although the range of the litter should be at the top end of the merit curve, and the best pup as good as, or better than, the parents.

"There is always a danger in talking in terms of tendencies and averages, that these will be taken as rigid and absolute. Part of the art of breeding lies in the selection of mates which will 'nick' with each other and produce offspring which revert little or not at all towards the average of the breed. Once the tendency or 'drag of the race' is recognised, the breeder judges his success by the range of merit in his puppies rather than by the production of a few brilliant individuals amongst a lot of duds. The importance of the worst puppy of each generation then becomes apparent; if the worst pups produced in the fourth generation of your strain are just as bad and just as numerous as the worst in your first generation you have made no real progress, even though you may have bred a champion. It is a good plan for the breeder of show dogs to give the worst pup in each litter to some neighbor as a pet, and to ask him to bring it to visit the kennels occasionally. Thus the breeder will not be allowed to forget its faults, and will have plenty of opportunity to compare it with the worst of later generations.

". . . Another difficulty in ordinary breeding operations is to establish a criterion of success. . . . The ordinary breeder cannot give equal opportunities to his dogs, and this is particularly true when the objective of the breeder is to produce dogs which will win prizes in the show ring. Wins depend so much on such things as the quality of the other competitors, the whim of the judges, the skill in preparing and handling the exhibit; every breed has had inferior specimens which have become champions through luck or influence, and brilliant specimens which never attained great fame. These elements, which we may call 'luck,' enter into every success which depends upon competition, but competitions for working ability have one great advantage over 'beauty' competitions: a really bad worker will never win consistently in working tests, even if his owner can 'pull strings.' The breeder of show specimens must therefore rely primarily on his own judgment of each animal, whilst the breeder of working dogs can safely rely on competitive success as a criterion of the quality of a dog, even if he has never himself seen the animal at work.

"Although the establishment of an above-average strain should be the objective of each breeder, commercial aspects of breeding exhibition dogs do not entirely encourage such a serious attitude. It is much more profitable to produce and sell one champion than half-a-dozen excellent dogs which just miss championship class. A good dog spoilt for show by one minor fault will sell for little more on the pet market than will a complete dud. Therefore, the common practice of purchasing a third-rate foundation bitch and sending her to the most popular champion stud dog of the moment is often justified commercially though not genetically: if one brilliant puppy results, the reputation of the breeder and even of his brood bitch will be established, even though all the other puppies were hopeless specimens. This is the fault of commercialism in dog breeding and will continue as long as dogs are bought and sold for shows. The serious breeder will only benefit financially if he can afford . . . (to) wait some years until he begins to reap the benefit of the high average quality of his stock. It is also difficult or impossible to establish and maintain a strain if the breeder is unable to keep a large number of dogs. Probably six adults and a varying number of young stock is about the minimum, and even then it would be very desirable to put a few additional bitches out on breeding terms as a reserve in case of heavy losses at home. The great majority of those who make a hobby of dog showing cannot keep sufficient numbers to establish a strain of their own. There is great opportunity for co-operation among small breeders, or between them and a larger kennel with an established strain. An agreed breeding plan and recording system can be adopted, experiences shared and mutual assistance given, each owner taking pride in assisting to develop a high average merit in the strain as a whole. Through such co-operation the smaller breeders could gain the greater numbers of dogs and increased capital which give the big kennel so many advantages; and at the same time their dogs, being distributed in twos and threes among co-operators, would get the personal attention and companionship which is inevitably to some extent denied to the kennel dog ....
"The foregoing recommendation on breeding methods . . . can now be briefly summarized in the form of a breeding plan for the foundation of a strain:

"(1) Decide on a few traits which are regarded as essential and on any faults considered intolerable. Whatever the breed, disease resistance, fertility, and absence of deformities, must be included as essentials, and certain character failings, such as viciousness, extreme nervousness, and hysterical or epileptic tendencies, must be condemned.

"(2) Develop a scoring system in which the selected virtues and faults receive marks in accordance with (a) their importance to your purpose or breeding aim, (b) their rarity or otherwise in the breed (or show population of a breed) as a whole. Virtues which are well-established in the breed and present in every individual used or bred need not be scored. As certain traits, rare at first, become established in the strain, their scoring may be reduced in order that greater weight and attention may be given to some other trait. Or the scoring system may remain the same, attention in mating being concentrated on scores for individual traits which require improvement.

"(3) Line breed consistently to the best individual produced until a better one occurs, then line breed to that. The blood of an outstanding dog or bitch can only be conserved by inbreeding to whilst the animal is living, but close inbreeding should only be resorted to when an animal of very exceptional qualities and with no outstanding faults is available. If inbreeding results in unsatisfactory litters this does not condemn the favored animal, but merely indicates that a less close mating should be made. Wide outcrosses should not be resorted to after the establishment of a strain, but some outside blood should be introduced, e.g., by the use of a dog sired by one of the strain from an unrelated bitch. In the foundation animals relationship need not be close, in fact wide outcrosses will give more variation and therefore greater possibility for selection of desirable combination of traits. Every animal to be used in the breeding program must pass rigid assessments for individual excellence as well as average excellence of its relatives including progeny when known."

For the dog breeder who wishes to improve a given strain of a given breed of dogs, the science of genetics has placed at his disposal the means whereby it can be done. A knowledge of the fundamentals of genetics, combined with patience and perseverance, will ultimately provide the discriminating breeder with that which he so ardently desires—dogs that are not only a delight to the eyes but that are genetically sound and that will consistently produce their own kind.

Are You Ready To Move Onto The Next Lesson? Click Here...