More about spotting

Ivy’s son Quechan carries only one copy of spotting but is heavily spotted: the belly, legs, underside of tail, and front of neck should all be black, and the fleece area should be gray. All of the white you see in these areas is due to spotting.

In my last blog, I talked a little bit about my current project, diving into trying to understand spotting in sheep. I’ve collected a database of nearly 300 lambs and have listed them by name, including sire and dam, and type of color. After looking at all of their birth photos, I have also cataloged every body part on which they carry white spots – a total of seventeen different body parts have been cataloged for each lamb. This is likely the biggest study into spotting in sheep that has ever been attempted – and it is getting more complicated by the day.

Yet this whole thing came about because of some of this year’s lambs – and that’s what I want to discuss a bit today. Some of my sheep are known not to carry spotting, so I expected that regardless of the other parent, their lambs would carry only the top of head and tip of tail spotting that the experts tell us is the result of a single copy of spotting at the spotting location. For example, our older ewe Ivy carries no spotting; I know this because not only does she not have any bright white areas in her birth photos that indicate spotting, but she also always gives us unspotted lambs when bred to a ram who doesn’t carry spotting. I bred her this past fall to Nahe, whose birth photo (or at least one of his birth photos) you saw in my previous blog. I expected the resulting lamb to have a white triangle on the top of its head and perhaps a bit of white on the tip of its tail. I did not expect what I got in her son Quechan, whose photo array you can see on the left. He is literally spotted from head to toe!

Quartz should have black legs, and a black underside joined to the chin by a black stripe, but spotting has turned him nearly white. Note the interesting symmetry on the legs!

And as surprising as Quechan is, I had many more such surprises this year. We have been told by the genetics experts that spotting is asymmetrical, producing random blobs of white anywhere on the lamb. When I bred Ossidy to Noa last fall, I knew that Ossidy carried lots of spotting – but again thought that coupled with Noa (who carries no spotting, as far as I can tell), I would get a lamb that had a white top of head and tip of tail that is supposed to be the expression of a single spotting gene. Instead, we got Quartz, who reminds me very much of Quechan, except that his spots are surprisingly symmetrical as you can see in the photos on the right.

Other lambs that I know can only carry a single copy of spotting are less spotted but still surprising. Quenby, the daughter of Phoebe x Nahe, and Qayden, son of Kaylen x Nahe each have dams who are not spotted, so all of their spotting must come from their sire, Nahe. Quenby should be solid brown without spotting and Qayden solid black, but notice that they each are surprisingly spotted – and in very different ways. Each of them is displaying the spotting they got from their sire, but I am having trouble figuring out why it looks so different in each of these two lambs!

Quenby should be solid brown, but spotting has given her several large white areas on her back half.

So, I’m on the hunt. Day after day, after I finish my chores outside, I sit down at the spotting database of lambs and sift the data, sorting by sire, then by dam, then by areas of spotting, etc. So far, I’ve made several discoveries, but I have yet to unlock exactly how this works – exactly how spotting from the dam and sire come together to produce what we see in the lambs. I now know that there is at least one additional location involved besides S, and I know that it only takes one copy of spotting at S to cause sometimes crazy spotting to occur in lambs. I have also determined that spotting is not recessive as we’ve been told – it is dominant. Yet, the exact mechanism – the list of rules by which spotting at this second location actually works – eludes me.

Qayden should be solid black with perhaps a white cap and tail tip, but instead, he is a good example of a heavily spotted lamb.

So, back I go to my spotting inventory. I know the answers are there – I just haven’t found them yet, but they are there. I know from experience that it only takes one idea – the right idea – to suddenly make all of this nonsense come together and make sense. Mother Nature is good at creating and following genetic rules; I’m just not quite as good at figuring them out – but I’m also not one to quit when I am this close. Eventually, I know that this will all make sense – and you will be among the first to know!

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7 Comments

  • Sue says:

    I think one of my favorite quotes from Dr. Phil Spondenberg (who I regard as the King of sheep color genetics) is that none of the rules apply when you’re talking about color in Romeldales. I know that’s been true with mine, and part of what I love about these sheep. Lambing season is like Christmas morning. I never really know what’s in that package until it’s opened!

    • Dee says:

      Well, I have much respect for Phil Sponenberg, but I’m thinking that either he was misquoted or misinformed, since we’ve been predicting the color genetics of our lambs for many years, now, and have few surprises except when it comes to spotting – and that is only because the basic understanding of the function of the S-locus has been poorly understood to date. After all, sheep are sheep, and sheep color genetics apply to the species and are not, in general, breed specific. The Romeldales do have a very wide range of patterns (more than any breed), and very much spotting, which makes them complicated, but not rule-breakers! If you ever want to be able to predict color, pattern, spotting, and the like in your flock, I’m happy to help you sort it out – just let me know!

  • Elaine Chicago says:

    This is just so interesting and I’m looking forward to more of these Spot Posts. I’m just an arm chair traveler and really enjoy all your sleuthing!

  • Janice says:

    Does the spotting remain as the animal ages? I know that Suffolk black lambs usually turn white as they near adulthood. What happens to the spots? Dumb question, I know!

    • Dee says:

      No, not a dumb question at all – a really good one, in fact! Traditionally, we have been told that spotting remains there for the life of the sheep – but we are finding that the traditional answer isn’t always true. I will have another post on Monday specifically about this question and what I have discovered. Stay tuned!

  • Jane M says:

    I have a really uninformed comment to make.. Years ago I read about three stripe patterns on zebras. If I’m remembering correctly the striping was all one gene and initially the stripes were all the same size. The pattern differences were all about when the stripe gene turned on in utero. So an evenly striped zebra had the gene turn on late and one with larger stripes on its haunches had the gene turn on earlier, and then the haunches grew a lot more. Don’t know if this applies at all to sheep…

    • Dee says:

      Ooh, interesting! I will keep this in mind in case it might be pertinent. Right now, I do think we might be onto something… I hope to know for sure soon!

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