F - WHAT?!

The generational percentages for Valais Blacknose sheep breeding programs are typically calculated based on the Valais Blacknose (VBN) purebred parentage. “Breeding up” refers to the process where each new successive generation has a higher percentage of the desired breed’s blood, in this case, the rare Valais Blacknose breed.  The typical progression of generational percentages in the process of breeding up to full Valais Blacknose is as follows:

  • The F1 generation refers to the offspring of an initial cross between a Valais Blacknose and another purebred sheep breed, resulting in animals that are 50% VBN.
  • F2 generation, the offspring of a F1 ewe bred to a purebred Valais Blacknose ram, would be 75% VBN.
  • In F3, the third generation, these are offspring resulting from the crossing of an F2 ewe back to a full-blooded Valais Blacknose ram. This gives us sheep that are 87.5% VBN.
  • The F4 generation would be the result of a backcross of to a F3 ewe with a full Valais Blacknose ram, resulting in offspring that are approximately 93.75% VBN.
  • Finally, the F5 generation is again a backcross, a F4 ewe to a full Valais Blacknose ram, resulting in sheep that are approximately 96.88% VBN. In the United States, these F5 sheep are considered purebreds and can be registered as such.

Keep in mind that these percentages hold true only for breed up programs that strictly follow this pattern, involving breeding with a full-blooded Valais Blacknose in each generation.  For example, we used a F3 “clean-up” ram after laparoscopic artificial insemination (LAI) earlier in our breed-up program which resulted in some F2.5 offspring (breeding a F2 ewe with the F3 clean-up ram).  In further generations, this F2.5 ewe bred to 100% purebred ram results in offspring at F3.5.

It’s important to remember that other factors such as genetic variation and dominance may affect traits in each generation. Our partners selected high quality registered Finn sheep as the starting breed in which to launch our VBN breed-up program.  Physical appearance might not always align exactly with the generational percentages.  For example, the Finn breed is white so it took longer for the distinctive black pattern to be fully expressed in some of the offspring in our breed-up program.

Here’s a table for the generational percentages in Valais Blacknose sheep breeding, from F1 to F5:

Generation                  Cross                      Valais Blacknose Percentage

F1                 Valais Blacknose x Breed A                       50%

F2                 F1 x Valais Blacknose                               75%

F3                 F2 x Valais Blacknose                              87.5%

F4                 F3 x Valais Blacknose                              93.75%

F5                 F4 x Valais Blacknose                              96.88%

This table shows the percentages of Valais Blacknose breed composition in each generation (F1 to F5) when consistently backcrossing with a purebred Valais Blacknose in each successive generation.