Typical Inbreeding percentages are as follows:
Father/daughter - mother/son - brother/sister -> 25%
Half-brother/half-sister -> 12.5%
Uncle/niece - aunt/nephew -> 12.5%
Cousin -> 6.25%
1. parent to offspring (mother-son, father daughter)
2. full siblings (brother-sister, sister-brother)
TIGHT LINE BREEDING
1. half-siblings (half-brother to half-sister)
3. aunt to nephew, uncle to niece
1. grandparent to grandchild (grandfather-granddaughter, grandmother-grandson).
2. a common ancestor on both sides of the pedigree within 3rd-4th generation.
(Sounds to me like grandparent or great grandparent to grandchild/great grandchild).
Understanding Line Breeding
There seems to be a vast misunderstanding about line breeding, what it is, why it is done and how it is done. Often one hears laymen and even some who should know better referring to it in derogatory terms and making the assumption that linebreeding is responsible for canine health and temperament problems. So in this article I hope to try to explain a little what responsible and knowledgeable breeders try to do in their breeding programs.
First let me be clear anything said in this article refers to reputable breeders who breed to develop dogs who are the best examples of breed type (what a certain breed should look like according to the breed's standard or blueprint) and are of sound mind and body. It does not refer to puppy mill or back yard breeders as the sole purpose of those sorts of breeders are to supply the most puppies as cheaply as possible for the most profit. Considerations such as breed type, health and temperament are of no interest to these people and any linebreeding or inbreeding done by them is merely happenstance and economically advantageous.
In the simplest terms there are three methods used when breeding purebred dogs: outcrossing, inbreeding and linebreeding.
Outcrossing is the breeding of dogs with no common ancestors, usually within a five generation pedigree. Continual outcrossing is a method that is commonly used by breeders who have no real purpose in breeding dogs or by novice breeders. Occasionally it is employed by experienced breeders to bring in some needed attribute to their line. Though one hears about such things as hybrid vigour when outcrossing, the continual use of this method can be as dangerous as continual inbreeding as you are always bringing new genetic equations to the mix.
Inbreeding is the breeding of close relatives not separated by more than one generation, i.e, brother to sister, father to daughter. This method is used to concentrate good qualities in the line but may also concentrate bad qualities. Only the most experienced breeders should be willing to attempt this method and be willing to make possible hard decisions with respect to the resulting puppies. Continual inbreeding should not be done.
Linebreeding is a method that breeders will use to improve upon and try to eliminate structural and health problems from their dogs. It is the breeding together of dogs that have a well bred superior common ancestor who has attributes that the breeder is attempting to reproduce and improve upon in their own dogs. Things such as health, longevity of life, structure, movement and temperament of a dog that one is planning to linebreed on must be taken into account. Linebreeding is an attempt to concentrate the genetic contribution of an outstanding ancestor in the resulting offspring. As well once started one must continue the linebreeding process or all will be for naught.
For a breeder who is contemplating linebreeding they must first study some basic genetics and learn how dominant and recessive genes affect the outcome of any breeding attempted. They must learn which attributes are dominant and which are recessive. They must also be aware of the genetic health issues for their breed and the mode of inheritance of those diseases. One must then study the dog that one hopes to linebreed on. Unfortunately in dogs it is not possible to know everything genetic about a certain dog as sometimes recessive genes may lie in wait but one can usually have a reasonable understanding of a dog's makeup through the study of pedigrees, both of the ancestors of that dog and his or her's offspring.