Issues, methods and limits
Inbreeding is a central concept in canine breeding. While it can be a tool for establishing certain qualities in a line, it also presents significant risks when used carelessly. In this chapter, we explain the main principles of inbreeding, its practical implications, and how we approach it in our breeding.
1. Essential definitions
– Inbreeding (strict inbreeding): this involves mating between individuals who are very close genetically (brother/sister, parent/child, uncle/niece, etc.). This method is currently not recommended in dog breeding, as it greatly increases the risk of transmitting recessive genetic defects.
– Linebreeding (consensual inbreeding): mating between individuals who share distant common ancestors, often several generations back. Used sparingly, it allows certain traits to be preserved without unduly increasing health risks.
– Outcrossing (or outbreeding): mating between individuals with no significant common ancestors over several generations (often 5 or 10). This increases genetic diversity and reduces the risks associated with inbreeding, while requiring vigilance over the morphological and behavioral compatibility of the lines
– Clarification on Linebreeding and notations 2-3, 4-4:
When talking about linebreeding, we often use a notation like 2-3, 3-4, 4-4, etc. These numbers indicate in which generation a common ancestor of the father and mother can be found in the pedigree. The first number corresponds to the generation on the father's side. The second number to the generation on the mother's side. For example: 2-3 on X means that ancestor X appears in the 2nd generation on the father's side (i.e. as a grandparent), and in the 3rd generation on the mother's side (i.e. as a great-grandparent). 4-4 on Y means that ancestor Y is present in the 4th generation in both branches. The closer the ancestor is in the family tree, the greater the impact of this targeted inbreeding. Too tight a linebreeding (e.g. 2-2 or 2-3) can quickly increase the inbreeding coefficient and should be used with great caution. In our breeding, we occasionally accept light and thoughtful linebreedings, particularly with breeders who have demonstrated excellent health, mental stability, and production quality. These crosses are always evaluated in parallel with the overall inbreeding rate.
2. Calculation of the inbreeding coefficient
The coefficient of inbreeding (COI) measures the percentage of genes inherited identically from a common ancestor by both parents.
It therefore gives an idea of the effective genetic diversity of the mating.
• A COI of 0 % indicates a complete absence of common ancestors.
• A COI between 6 and 8 % is tolerable in certain lines.
• A COI above 12-15 % is considered too high and a source
of significant risks.
The FCI recommends staying below 6.25 % over five generations (which corresponds to the union of two first cousins).
In our breeding, we choose to be even more rigorous: we aim for an inbreeding coefficient of less than 3.5 % over 5 generations. This precaution helps maintain a solid and healthy genetic base.
Morphological comparison between a young female dog produced by Des Crocs Véritables and a female dog from the DDR line from 1974
For this, we use specialized calculation tools that take into account the entire pedigree over 5 to 10 generations.
3. Risks associated with excessive inbreeding
Too high an inbreeding rate can lead to:
• An increased risk of genetic diseases (especially undetectable recessive diseases)
• A general loss of vigor: slowed growth, weakening of the immune system, reduced fertility
• A reduction in the diversity of the immune system, increasing susceptibility to infections
• The appearance of behavioral disorders or nervous fragility
4. Our approach to inbreeding
We have chosen a reasoned approach, combining selection and preservation:
• We favor matings with a low inbreeding rate, below 3.5 %.
• We use moderate linebreeding only if an ancestor has exceptional qualities that we wish to establish (without repeating the same name several times in a close pedigree).
• We also practice genetic renewal by outcrossing, by introducing compatible external lines, to strengthen diversity without compromising the desired type.
• We never breed two healthy carriers of the same recessive disease.
5. The most frequently used analysis methods
Here is a simple explanation of the three most commonly used inbreeding indicators to assess the impact of an alliance (e.g. on the site WorkingDog) :
1. Consanguinity coefficient (CS) or also called Consanguinity rate (CR)
What it measures:
The probability that a dog will have two identical copies of the same gene (homozygous) because its parents have one or more common ancestors.
What is it for:
The higher this number, the more inbred the dog is. This means greater genetic homogeneity... but also an increased risk of genetic diseases or loss of diversity.
The formula used:
They use an approximation based on the proximity of common ancestors in the pedigree.
The formula: CS = sum (1/2)^(n1+n2+1) Or n1 And n2 are the generations that separate each parent from the common ancestor.
2. Implex coefficient (IC)
What it measures:
The rate of repetition of ancestors in the pedigree.
A CI of 100 % = no ancestor occurs multiple times.
A lower CI = some ancestors are present several times, therefore less genealogical diversity.
What is it for:
This indicates how many distinct ancestors were used in the lineage.
A low CI = the same dog is used often in lines (which may be desired to fix traits, but increases the risks of inbreeding).
3. Inbreeding on the line
What it shows:
Which dogs appear on both the father's and mother's side, and in which generations.
What is it for:
This is a convenient view for identifying common ancestors in the intended alliance.
This allows you to see exactly where inbreeding begins in the pedigree, and with which dogs.
CS, CI and inbreeding on the line
