The old adage of breeding the best to the best is good sound genetics but it is important that breeders know what the best is. All to often breeders are inclined to think that the best are the dogs which they own. If breeders are right then they will make progress by breeding from these dogs. If, however they are wrong then breeding from such animals will ultimately retard progress. Since much of what is considered good is decided in the show ring, it is imperative that judges do indeed select only the best specimens since it is from among the leading winners that most breeding selection will take place. Judges therefore have a crucial role to play. If judges are not skilled, they will inevitably give high awards to the wrong dogs and could therefore lead the breed down the wrong road. The same is true if judges either cannot assess or if they ignore weak characters and thus allow fearful or, worse still, overly aggressive animals to win. Breeders are not, of course, obliged to follow judges and skilled breeders often will not. But most dog breeders are involved for relatively short periods of time (five to seven years) and many will follow fashion simply because they are not knowledgeable.
A breeder, in whatever breed, has to formulate an idea of what it is he or she is trying to achieve. To do this, a breeder must fully understand the breed Standard since this should form a blueprint for the ideal dog being sought. However, character as well as construction must be considered since the majority of dogs are sold to pet owners and for them a sound character is, in the long term, more important than mere physical beauty. Owners have to live with the real dog not the prizes it has won.
Of course, no dog is perfect and inevitably breeding takes place using animals which might fail in a particular feature while excelling in others. The dog breeder must use a system of selection to which he or she can easily adhere. The principal one used by breeders involves independent culling. Using this technique, the breeder sets a specific limit for a series of important features of the dog below he or she will not go. It might be decided for example to breed only from males that are at least 25 inches/64 cm in height; that have well laid back shoulders and a chest depth that is one-half of the wither height. These might be some of the criteria set. Each dog would be evaluated against these standards. Those falling below the required minimal level in any one feature would be eliminated from breeding. Thus all breeding stock will meet a certain basic minimum level of excellence.
Clearly the more traits that are listed and the tougher the imposed limits, the more likely the breeder will find that all dogs will fail in something. It is important that breeders set a sensible and plausible standard in each trait and that only really important features are sought. There would, for instance, be little logic in culling an otherwise outstanding animal simply because its eye color was slightly too light. Given sensible standards and a limited number of attainable goals, a breeder will be able to make progress depending upon the extent to which the traits involved are heritable. In most breeds only about ten percent of males and thirty percent of females are used for breeding, so a high proportion of dogs are not and should not be bred from at all - no matter how much a breeder might like to have a puppy from a favorite pet.
There is an element of luck involved in all dog breeding but the better the breeders' knowledge and understanding of the Standard and the greater their ability to recognize merit (and shortcomings) in examples of the breed concerned, the more likely they are to succeed. The breeder who cannot distinguish, for example, a correctly laid scapula from a forward-placed one is going to run into difficulties sooner or later and breed from inadequate stock, creating poorer shoulder construction as a consequence.
In polygenic traits such as most conformational aspects there is some truth in the view that like begets like. If tall animals are bred from then, gradually and perceptibly, the breed will get taller. If early maturing animals are bred from by using those animals which appear "finished" while still only puppies or yearlings, then the breed will become more early maturing. These things occur because the genes involved have a collective influence even though the individual genes are not in themselves very important. The more heritable the trait examined and the greater the selection practiced, the more successful selection will be in moving the breed in a given direction. Very often breed advancement does not occur but this usually is because breeders are not all selecting for the same things or not all in the same direction.
Certain anomalies need to be considered depending upon the breed. In breeds where hip dysplasia is know to be a definite problem, breeders are required to have their potential breeding stock assessed through the appropriate scheme such as that of the British Veterinarian Association/Kennel Club in the United Kingdom, the Orthopedic Foundation for Animals (OFA) in the United States or the Australian Veterinary Association (AVA) in Australia. Most countries with kennel clubs have recognized schemes and dogs which do not measure up well to breed averages should be discarded. Similarly, if progressive retinal atrophy is known to exist in the breed all would-be breeding stock should be eye-tested every twelve months during their breeding life and culled from breeding if they fail. A German Shepherd Dog breeder should not use a male until it has been cleared for hemophilia A. In the same way a Bernese Mountain Dog breeder should not be using dogs that have not had their elbows checked through a recognized scheme. These are necessary rules of thumb that breeders in specific breeds need to apply if they are to breed litters which they will sell to others.
Progress in hip dysplasia control is often slow despite the fact that in some breeds the heritability is around 40 percent. The fault lies not with the inherited nature of hip dysplasia or even failure to screen dogs but rather from the fact that, having screened animals, some breeders still breed from the dogs that are worse than the breed average or they continue to use sires which have been shown to be producers of poor hips.
When considering an individual mating, both sire and dam are equally influential though one may offer "better" genes than the other. However, in considering breeds as a whole, sires are generally much more important than dams. This is because fewer sires than dams are needed and thus potential for selection is greater through sires. In most breeds it is probable that about seventy percent of progress will stem from the selection of sires. While it is undoubtedly true that bitches are the strength of a kennel, it is equally true that careful attention to the selection of the very best sires will bring about the greatest advances.
In the case of simple Mendelian traits, like does not necessarily breed like. For instance, if two smooth-coated Chihuahuas are mated they could give rise to some long-coated progeny if both parents are "carriers" of the long coated gene. If the smooth-coated gene is designated as L and the long coat as I then smooth-coated dogs can be either LL or LI but long coats are always II. The table below shows the results which might occur from various combinations of matings. Although this applies to smooth and long coats in this instance, the basic rules apply to any simple Mendelian recessive trait.
In the table the percentages are accurate in matings 1, 3 and 6 but in the other three the percentages only apply given sufficient numbers of animals. Note that because short coat is dominate to long coat it will totally mask long coat so that LL and an LI animal would appear identical to look at as far as coat length is concerned. Note also that only when gene I is carried by both parents can long-coated stock result (matings 4, 5 and 6). The most usual mating which brings to light a hidden recessive is mating 4 when, perhaps unwittingly, a breeder mates together two carrier animals resulting in some 25 percent (on average) of the pups showing the recessive trait. In the case of long and short coats these may both be acceptable in some breeds but in the case of other traits the equivalent of long coat may be undesirable. There are many such traits in the dog ranging over coat color, eye disease and a variety of other anomalies.
|LL (short)||LI (short)||II (long)|
|1) LL x LL (short x short)||100||0||0|
|2) LL x LI (short x short)||50||50||0|
|3) LL x II (short x long)||0||100||0|
|4) LI x LI (short x short)||25||50||25|
|5) LI x II (short x long)
|6) II x II (long x long)||0||0||100|