Methods of Breeding
There are four types of breeding; inbreeding, line breeding, out crossing or out breeding, and backcrossing. Each type has its purpose when properly used. There is a difference of opinions among breeders on the exact definition which is probably due to the differences in the breeding methods used on different species. Inbreeding in dogs is much different than inbreeding in humans. This comparison would be much confusing to the lay person. Why would you breed a father back to her daughter? Isn't that "incest"? When talking about people, the answer would be a resounding "YES"! With dogs, there is no social taboo or inhibition.
Within a pack of wolves, there are only two different classes; "alpha"- the ones that are allowed to breed or "betas"- the ones who may or may not breed depending on the "alpha's" wishes. Familial relationships don't enter into their view of things. This would be disturbing to humans, but it doesn't matter to dogs. As a dog breeder, decisions have to be based on genetic makeup of the dogs, first and foremost. The dogs see the breeder as "alpha", allowing or disallowing breeding as the "alpha" dog within a wolf pack would do. This canine trait has allowed humans over hundreds of generations to alter the physiology and temperament of the dogs which lead to the domestication of the dog, change their appearance and abilities.
Inbreeding
One of the most hotly talked about topics with regard to pure-bred dogs is the use of in-breeding. This is a term that is often misused and is extremely misunderstood. Part of the misunderstandings comes from differences in the way the terms are used within the scientific/medical field, and how it is commonly used by breeders. (Read The Myth of Canine Incest)
One of the common misconceptions about in-breeding is that it causes genetic diseases. Breeding closely related animals does increase the possibilities that any bad genes within a line will show up, but it does not ‘cause genetic disease. Purebred dogs have a smaller gene pool to draw on than mixed breeds. That smaller gene pool is what gives its individual characteristics, such as physical appearance and temperament. It is what makes a German Shepherd show dog a show dog and old style German Shepherd the old style German Shepherd. (Read The German Shepherd breed)
Inbreeding is more likely to help "set" or "fix" a particular trait within a breed or line by narrowing the gene pool to favor those traits. If a breeder is looking to set a particular feature of their line, then choosing the offspring most strongly possessing that trait can be beneficial. The mating of related dogs (no more than two generations removed from another) is inbreeding. By this definition, the most distant related dog would be those having only one grandparent in common. The exception of this rule would be the mating of mother to son or granddaughter to grandfather, ect. This will be explained later under line breeding. Much easier inbreeding can be obtained by breeding brother to sister through several generations. Slight inbreeding for several generations may have a greater effect than close inbreeding for one generation.
This method of breeding brings out recessive genes in the homozygous condition. "Homozgous" are genes that have no opposing gene. The dog will carry this trait and no other opposing trait. If white fur is homozygous, then they only have the gene for white fur and pass this strong trait to its offspring. The results obtained from inbreeding depend on the recessive genes carried by the original animals. The recessive genes are genes hidden by the obvious visible traits, but the dog still carries still carries this trait. The hidden genes could be either good or bad, but is being overshadowed by the more dominant trait.
Dr. Helen Dean at the Wister Institute in Philadelphia has proven most definitely that inbreeding has no bad effects. She bred rats, brother to sister, for over a hundred generations and the rats were larger, lived longer and produced larger litters than when she first began her experiments. Careful selection was practiced throughout the experiment and the undesirable animals weren't allowed to breed and only the best were kept. If a line of dogs carried an undesirable gene, it must be removed from breeding or it will continue to appear in future generations. Inbreeding accompanied with careful selection using Wright's COI (Coefficient of Inbreeding) is one of the best possible means of breed improvement. Slight inbreeding is practiced by most dog breeders and serves to maintain stock uniformity and keep the children similar to parents and general ancestry.
One of the most inbred lines of dogs in the world has the lowest breed incidence of hip dysplasia and the highest success rate as superior companion dogs--the seeing eye German Shepherd.
Line Breeding
Another way to help "set or "fix" desirable traits is by using line-breeding. You still breed dogs that are related but you are also routinely introducing genes from other lines into the genetic mix. Fixing the desirable traits takes longer, but it lowers the risk of problems associated with repeated in-breeding. With tight line breeding you might find 4 or more dogs showing up numerous times within a 5 generation pedigree. Loose line-breeding over successive generations will result in more variations of physical appearance than "in-breeding" or tight line-breeding, but it will keep the physical structure of size and shape with fewer long term risks.
Line-breeding is just another form of inbreeding that has been over-publicized, depending on whom you talk too. Just like inbreeding, the results obtained depend entirely on the quality of the original stock, skill with which the breeding program was planned, executed, methods and amount of selection. There are dozens of line breeding theories, plans, charts and schemes propose. Some of these plans are touted as a general cure-all for the elimination of faults, while other schemes profess to breed champions from common pet stock.
"Not all good dogs are champions, and not all champions are good dogs". (This is the German Shepherd by Capt. WM Goldbecker)
The Line-breeding program should always be planned to fit the individual case. Any plan which is meant for one breed or one dog as another won't be of much value. A breeder shouldn't go to the "big name" because he's a show winner. Sometimes the best dog for a particular Dam can be an unknown dog with specific traits to compliment her. Some "theories" have become quite popular because the advocates claim are always pointing to this or that great dog was bred according to their theory. Breeding methods are used to cull bad genes in hopes of retaining the good and assist in producing healthy, good temperament dogs. Everything else should be second. There is no quick answer or some super stud dog that can fix all the breed problems instantly. There is no plan that is guaranteed to produce a champion- however the chances of increasing the odds of the millions of genes in such a way to produce overall quality is through careful selection and a breeding program which fits the individual.
The strongest possible effect is to breed the sire to his daughter over several generation, but this method is even capable of producing youngsters which don't hold the exact genetic composition of the original sire. Also recessive genes still appear but in a more orderly manner and less variation than inbreeding. The breeder can choose, to some extent, which recessive gene he wishes to bring out and which ones he wishes to hold back. (Read Basic Linebreeding)
Out Crossing
The mating between individuals who show no common ancestor in a four generation pedigree is called out crossing. This method is used to bring a new trait into an inbred line or to increase the amount of variation for future selections. A phenomenon known has hybrid vigor is closely related to out crossing. When an out cross is made to a different strain, the crossbreds often prove to be superior to either of the original strains. This is why so many show people feel this is a good method; by chance it could net them a big winner.
Hybrid Vigor does not always occur and there is little chance in predicting when or will it occur. With continued breeding, the advantages could be lost and the pups because the homozygous genes have been "watered down" and there is a tendency for a breeding group's progeny to return to mediocrity. So back-crossing to a common ancestor from a previous generation might be needed to retain the Hybrid Vigor.
The best option for breeding dogs is generally line breeding, with occasional instances of out crossing and inbreeding to gain or eliminate specific traits. A wise breeder will use all of these methods carefully, reevaluating his breeding program as pups grow up and planning future bleedings with these methods in mind to refine and bring out traits he feels are important, and lessen traits he feels are a detriment. (Read Animal Genetics)
Next Topic- Puppy Genetics