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No Such Thing as a Dominant White?

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If any of the assertions below contradict what you believe about alpaca base coat color genetics, it’s definitely worth reading this blog post and continuing on to a very friendly, fun-loving statistical analysis that is available in our website’s library!

1. First, all white alpacas can produce color when they are bred to it. There is no such thing as a homozygous dominant white animal.  In fact, a pink-skinned white is in some ways as recessive a creature as a true black.

2. What’s more, many fawns are not just “dilute” but carry a white base coat color allele, which acts to dilute a brown allele in the production of the phenotypic coat color. You can actually breed two fawns together and get a homozygous white.

3. White breeders, no need to rely on those pure-white pedigrees to make sure you don’t produce fawns and browns. Turns out a brown allele can’t really hide itself well phenotypically.

4. Color breeders, to introduce white genetics into a color breeding program with lower odds of producing white offspring, breed that white animal to brown. The darker, the better.

Now, if you are like me and lack an educational background in genetics, it may also be true that, like me, you find it hard to wade through genetic research on alpacas.  In my case, I can sometimes remember a conclusion from a genetics paper for only a few hours after I read it.  Sad, but true: Ask me a few days later and what I remember about the paper is likely to be “It had a lot of letters that didn’t make words.”   Lacking an intellectual framework for understanding the research, I have had trouble retaining what genetic research I have read long enough to evaluate it in the context of my own experience, let alone incorporate it into my breeding strategies.

However, I do have an antiquated background in statistical modeling! (Insert half-hearted cheers.) And I brushed the cobwebs off of it a few weekends ago to analyze an observation that had been vexing me:  Why, if white is supposedly the “dominant” alpaca color, do I not see large numbers of whites in my own herd that cannot produce color when bred to it?  In fact, I see the opposite.  All of my white whites seem happy to produce color when bred to it, even with deep, multi-generation white pedigrees behind them.  How can this be?

I used basic probability analysis to demonstrate that this outcome is incredibly unlikely if the white base coat color allele is dominant over brown and black, as many of us were once taught.  Then I went back to review Kylie Munyard’s 2011 research on alpaca coat color, and found that she posited a incompletely dominant white allele, along with several other conclusions that came as a complete surprise to me, even though I had previously read that paper several times (I told you.)  Long story short, I found that they fit existing multi-generation color production data better than the classic dominant white/dilution theories do.     I also found they opened doors to new breeding strategies.

I wrote about these findings for a blog post, but the write-up ended up a bit too long for this format.  So I have posted this analysis on our new research library page on our website, (see the tab above, or follow this link Evaluating Genetic Color Hypotheses) along with Kylie Munyard’s 2011 paper.   If the assertions at the start of this post were surprising and/or of interest, read the analysis in the library for more information.  I especially recommend this for breeders of fawns and whites.