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Sheep Color Genetics

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My interest in sheep color genetics started when our first lambs hit the ground in 1999. We bred our ewes to a moorit (brown--see color terms for definitions of color genetics terms as I use them.) ram and had six moorit lambs, apparently. But on closer observation, Shaltz Farm Allana had nearly white wool at the skin under brown tips, when she was born.

Needless to say, Allana was a puzzle. I had already dug into rabbit color genetics a bit, genotyping around 200 rabbits in the process, and figured that sheep couldn't be much trouble to figure out, right?

natural shetland colors
Black, Shaela, Moorit, Gray, and Fawn can be seen in this photo of our rams eating some grain.

Wrong! There are thousands of years of breeding color out of sheep behind us, leaving only 'primitive' breeds like Shetland and Icelandic routinely expressing color in their wool. And research on sheep color genetics is slow because most ewes produce one or two lambs a year, not the several dozen kits a rabbit doe can produce. No wonder sheep color genetics are not well understood, especially when you consider that it's only in the last 20-30 years that the 'black sheep' of the flock hasn't been a liability to the shepherd.

With the help of a number of references such as the Internet mailing list,, and some publications I was able to buy or borrow copies of, things got muddier instead of clearer. There are different mechanisms for color in primitive breeds of sheep as opposed to modern breeds, for example. I was really convinced of that when our black Border Leicester ewe, bred to a moorit Shetland ram, produced a black twin and a white twin! In Shetlands, that's not possible.

What's a poor befuddled breeder to do? If you think you might be interested in some frustrating but fascinating logic puzzles, these pages will hopefully get you started with sheep color genetics.

If you are new to any kind of color genetics, try my Primer of Color Genetics. It's a very basic introduction ideal for folks with an interest but no background in genetics. Yes, I've probably oversimplified a bit--feel free to email me, with your critiques. If I can make this primer more accurate without sacrificing clarity, I will be glad to do so.

If you raise Shetlands or Icelandics and are interested in the traditional color genetics theories based on Adalsteinsson's work, check out Genetics for Shetland Color for my interpretation of his work as it applies to Shetlands.

If you raise a typical modern breed such as Border Leicester or Romney, an 'extension' (pun intended :) of standard genetics will help you out. Read the Primer of Color Genetics, then Other Colored Sheep for a basic explanation of the black sheep in your flock.

Finally, some of the references I have used in coming to my understanding of sheep color genetics. It's a complex subject, and I keep going back to the materials I have to try to understand what's happening in my flock and others I've heard of.

There's far more left to be figured out than these pages will touch on. Why are some brown sheep moorit, and others dark brown, for instance? Why do some sheep show a lot more pheomelanin than others? Can we breed to retain that lovely 'apricot' color? I hope to hook up with other breeders interested in these questions--again, email me if you're interested in recording your breedings in a way we can put together to figure out more about sheep color genetics.

So, is this a hobby, or an obsession? Do I belong in the nuthouse? OK, so I eat and drink and sleep and dream color genetics each spring! But I can still function. Most of the time. As an Awt/Aa, I think. But when the dreams get going, I'm definitely an Ag/Ag.....

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