Woodland Creek Soay Rams

Woodland Creek Soay Rams
Soay Sheep Ram Assortment

Tuesday, April 6, 2010

Lambing update - Self-colored Light phase

We had our 6th lamb a few days ago - a "Black and White". Disappointly little white, given the parents (WC Yosemite and WC Anasazi). The ewe lamb (Ash) has only a "twink" of white (as Kate Montgomery called it).
Woodland Creek Ash '10 ewe
But today we had two more lambs-these from our line attempting to produce the very rare self-colored light phase (self-light for short) NA Soay. Given the non-existence of these in North America in previous years, I had been working toward creating some. One route to this is to breed self-dark (i.e., solid black) Soays with light-wild Soays. Given that the self-colored parent MUST contribute the recessive Aa, and the light phase parent MUST contribute a recessive Bb, the offspring MUST have at least one copy of each of these. In 2008 I did a number of these breedings, and produced 4 ewes and 2 rams of this genotype A+/Aa, BB/Bb. Of course they all look just like "regular" Soays - all dark-wild. But breedings of these genotypes have a small, but finite, probability of producing the elusive self-light.
Of course the odds are not that good. Below is a table showing the possibilities for mating two "half-SCLP" Soays.
You can see that when I bred my four "1/2 SCLP" ewes last fall to a "1/2 SCLP" ram, there was only a 1/16th, or 6% chance of a SCLP. Well, today two of those 4 ewes lambed, and for a moment I was convinced I had hit the jackpot with one. Check out Tahkenitch's ram lamb.
Tahkenitch's ram lamb '10

When I saw the uniformity of color on the legs, belly and under the tail i thought we had gotten very lucky. Closer inpection, though, revealed the telltale light spots around eyes, under chin, and inside ears. Alas, he is not self-colored. He does, of course, have white spotting as both his dam and sire (Sequoyah) do as well.
The second lamb was, as the odds would have suggested, also phenotypically a dark-wild pattern.
Molly's ram lamb '10
A nice enough lamb, but not what I was hoping for! Note that the trouble with breeding for SCLP in this manner is that the genotype of the lambs, for the great majority, will be unknown. Mostly one will get dark-wild lambs with unknown genes for the second allele at both agouti and brown locus, so they can't really be used to further the cause for SCLP. This particular breedign goal may be a hopeless endeavor given the flock size I can realisticall maintain. Given that I have (and can keep alive!) some actual SCLPs, I have a "sure" thing for next year, and very good odds with the SCLP ram as sire, so I will probably go that route.

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