Color Genetics of Gotland Sheep in North America
by Franna Pitt, PhD
Copyright, 2007
Conclusion
Now that you've reached this page, do you think you're better able to choose
Foundation ewes for your future Gotland flock? Do you think you are better able
to identify the genotypes of your percent Gotland lambs?
Some things I try to keep in mind:
- Avoid Aa, solid sheep, and Ag grey sheep for foundation ewes. Agg/Aa and
Agg/Ag sheep are indistinguishable in phenotype from Agg/Agg sheep. Since
the goal is Agg/Agg sheep, selecting away from Aa and Ag in the percentage
Gotland sheep will be very difficult. Better to leave them out to begin with.
- Breed out Extension dominance. However, an ED ewe can be useful, especially
if she's AWt/AWt under that ED mask. At worst, her AI lambs will be ED/E+
Agg/AWt, and their white AI offspring will be E+/E+ Agg/AWt - one AI step
away from E+/E+ Agg/Agg grey lambs.
- Don't mess with brown Foundation ewes (unless you don't mind brown surprises
in several generations). There is no way to reliably test breed or eliminate
the recessive Bb allele. Some day maybe there will be a genotype test as there
is in dogs, but that's not the case today.
- Avoid ewes with heavy phaeomelanin (tan) if you want blue-grey Gotlands.
- Use sheep with spots judiciously in your breeding program. You'll need to
be careful to avoid letting spots get too large and slide into the wooled
areas in subsequent generations.
The 4 color genes that have been discussed - A, B, E, and S - are only 4 of
millions of alleles that make up the complete genotype of your Gotland percentage
sheep. I hope that this discussion has made it easier to achieve the desired
homozygous Agg/Agg BB/BB E+/E+ Gotland sheep in North America. The selection
of other traits is up to you.
- Franna Pitt, PhD
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