Go Pitbull Forums banner
1 - 3 of 3 Posts

·
OCD Bullyologist
Joined
·
8,663 Posts
Discussion Starter · #1 ·
The Strategy of Breeding
Linebreeding, Inbreeding and Outcrossing

Inbreeding
Inbreeding seems to scare the beejabbers out of some people. For those people who cannot destroy defective dogs, it should. For those serious breeders who can cull and carry on, it will eventually become an option. It is an extremely useful tool for diagnosing what genes are present. If the genes for bad eyes are present, but hidden or recessive, this will bring them out to their full extent. If there isn't any bad genes, then the puppies will be of very close uniformity and very able to reproduce themselves (theoretically).The resulting puppies will have a lot of genetic material that is the same as their parents and grandparents and will be close genetically to each other.
What is meant by inbreeding is this; breeding two dogs that are closer than cousins. Typically thecombination are brother/sister, father/daughter, mother/son, and on the looser side, cousin to cousin, grandfather/granddaughter, half-brother and halfsister. You get the idea. The dogs should have or be common ancestors. People disagree about the exact point at which inbreeding becomes linebreeding but inbreeding is the quickest way to find out what poor genes are in the line and what dominant characteristics are in the line.
Genetically what inbreeding does for you is concentrate the traits in your stock, both good and bad and that is stressing good and bad. The bad is as important as the good. While you are fixing all those good traits in your population, a hidden trait may crop up that can wipe you out if you aren't careful. This is the down side of inbreeding. When those traits appear, the affected animal must be removed from the breeding program.
Inbreeding doesn't introduce new genes and does not eliminate bad genes that the line already has. It only shifts them around like a rubix cube. This often results in litters with high show potential, if the quality was high to begin with. It shows you what recessives you have lurking in the dogs' backgrounds, both good and bad. But there are drawbacks. Besides the possibility of bad recessives, inbreeding exclusively over time will eventually lead to infertility. It's like a xerox machine. After so many copies, you have to renew the ink. The same with dogs, you have to introduce new genes. No reputable breeder will use inbreeding exclusively, and many breeders simply never use it.
Inbreeding increases homozygosity and decrease heterozygosity. Homozygosity means that certain traits will double up so that no matter what the dog is bred to it will carry on those specific traits. Heterozygosity means that more genes will be in a single dose and less likely to show up in any given trait. So inbreeding can duplicate both desirable and harmful genes, both of which can be unsuspected in the line, and may appear. Inbreeding does NOT create anomalies, it brings present anomalies to the surface. Even when the anomalies are present, inbreeding might not reveal them. However, once revealed, then the breeder can do something about them in the next generations of breeding.Usually, you will only find: very experienced breeders, ignorant breeders, and puppy mills making use of this technique.
Let's say that you've been inbreeding for a couple generations and you now have a genetic defect in your entire breeding population. Keep inbreeding, looking for those one or two clear animals and use them because they are almost exclusively clear of the problem. An increase in harmful recessives is undesirable but it is not a major drawback if they are identified early. The effect of inbreeding on major polygenic traits is greater. Generally, traits that are highly inherited or ones which are many genes added together to produce the defects, are not adversely affected by inbreeding but, traits under non-additive control, especially those tied to dominance and not of high heritability, are often markedly harmed by inbreeding.
Inbreeding is not for the faint of heart or those unwilling to keep their pups long enough to make positive assessments. But for those who are breeding with a goal in mind, it gives them much greatercontrol over their gene pool and a direction to head towards knowing what exactly they are dealing with in their dogs.

Line breeding
Line breeding is when the sire and the dam are distantly related: grandsire to granddaughter, granddam to grandson, second cousins, half cousins, uncle to niece, aunt to nephew. The general strategy is that there is a common ancestor that is being doubled up on both sides. So the desired dog appears several times in the pedigree which is of excellent quality in every way.

This is probably the most common strategy in breeding purebred dogs (and in developing new breeds, for that matter). Through this method, new genes are slowly introduced and unwanted genes are slowly replaced. The actual rate varies by how strongly you line breed. It sacrifices little overall quality in terms of show quality. Usually the puppies are rather close in general conformation. The only problem with this method is that it often takes several generations to get poor genes out, (or adding desired genes in) resulting in many puppies that have the same genetic problems (or virtues) that their parents have. And then because some breeders are more interested in winning, they do not place the affected puppies on spay/neuter contracts. This is both a blessing and a curse for the breed. If the breeder is very careful, affected pups can be used wisely to prevent loss of quality, but still remove the affected genes by only breeding the affected pups to known non-carrier relatives. This way the breeder can again try to "edit out" the bad genes. This process results in dogs that will often reproduce their same level of quality. This is referred to as reaching homozygous litters (more genes of the same kind apparent in the puppies) and thus more uniformity.
Inbreeding and linebreeding really differ only in degree. Linebreeding is less likely to cause harm than inbreeding. Inbreeding is not for novices. Knowledge of genetics and the breed is required for success. For good results it must be well-planned and breeders must be ready for whatever problems it presents.


Outcrossing
Outcrossing is where the sire and dam are totally unrelated, preferably for three or four generations. The true form of an outcross is between two entirely different breeds because in reality the members of most registered breeds come from a common ancestor (although it may be many, many generations back). It is very rare for outcrossed puppies to be uniform in appearance. Usually there are a very large ranges of sizes, coats, colors, markings, and other distinctive characteristics. Outcrossed litters are generally heterozygous, and do not reliably reproduce themselves, so even the nicest puppy in the litter may not produce the best puppies.

Outcrossing is generally used to introduce something new to a line -- a better head, better colors, better front, etc. Usually the puppies retained from these breedings are bred back into the breeder's original line to standardize them back into the line's general characteristics and reproducibility -- with the one desired characteristic. The tricky part is that other characteristics may come along for the ride!
If you are dedicated enough, you can eventually continue breeding by outcrossing alone (but don't expect instant or quick results). You should pick dogs that complement each other well and are similar in general appearance. This is a long hard road to eventually developing a line. Through outcrossing, many health problems can quickly be eliminated (or just as quickly added into your breeding), but usually you do sacrifice some show quality and producibility.
You have to remember that dogs that appear totally healthy may be carriers of genetic problems. To find this out, test mating is done to a dog that is affected with the genetic problem (resulting usually in puppies that are both affected and non-affected carriers) or by inbreeding to a related dog that also doesn't show the signs of being affected (usually littermates are used) this will usually result in some puppies free of the problem, some puppies as carriers, and some puppies affected. By breeding two dogs that carry the problem you may have to put all the puppies down).
There are variations on outcrossing. A "true" outcross could be a dog that has totally unrelated dogs bred together throughout the pedigree. This is very rare. On the other hand, "linecrossing" is a form of outcrossing unrelated lines are bred to produce a new line. The sire and dam are usually very linebred from their prospective lines and the resulting puppies are varied in appearance, some looking like the sire's line and some looking like the dam's line and some looking like mixtures of both lines.

Strain

A strain or Line is a family of dogs with a set of traits chosen and developed by the breeder that will exclusively reproduce themselves by way of pre potency in the parents. Both parents will be homozygous for the particular traits that you have chosen and will reproduce the same way.
 

·
The Yard Of Many Colors
Joined
·
3,420 Posts
:thumbsup::goodpost:
 
1 - 3 of 3 Posts
Top