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Inbreeding Genetic Principles

Inbreeding is the result of two related animals mating. Inbreeding occurs when the same ancestors are found both in the paternal and the maternal lines.

The progeny's inbreeding level depends on the degree of relationship between the parents.

Mating results with a coefficient above 6.25% are not recommended if you wish to maintain reasonable inbreeding levels in your herd or in a given population.

Generally however, low inbreeding does not bring any problem. Inbreeding levels are considered low if there are five generations separating the two common ancestors,  ((1/2)5 x 100 = 3.12%).

        

 Remember: inbreeding is not hereditary!

  • Two highly inbred individuals with no common relatives will produce non-inbred progeny which will benefit from hybrid vigour.
  • Two non-inbred individuals with common relatives will produce inbred progeny.
  • Examples:

    Aerocerf (15.3% inbreeding) x daughter of Leader (not related to Aerostar) = 0% inbreeding
    Stormatic (low inbreeding) x Comestar Lausan Black (low inbreeding) = 25% inbreeding

By a visit to the Canadian Dairy Network Website at www.cdn.ca, you may determine the inbreeding level of a selected mating. Choose «Inbreeding calculator» while having on hand the registration numbers of the animals you wish to mate.     

Example 1 - One common ancestor    


        

 

 

In this example, the common ancestor Emory is found to be separated by 4 generations. The calculation to be done using the formula above is:

       

Example 2 - Two common ancestors    


  

     

In this example, Storm and Aerostar are found to be two common ancestors separated by respectively 4 and 5 generations. Here is the calculation to be done using the formula above:     

       

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