We are more than halfway through lambing, with 26 lambs from 18 ewes, and 13 left to go. We haven’t lost a single lamb or had any still-births, but we have had quite a run of singles, which is very unusual for us. Only 8 sets of twins from the 18 ewes, and 10 singles. We are not sure why; it may be that our nutrition was not quite high enough at breeding time, as we were trying to keep our easy-keeper ewes from getting fat. Next year we will probably flush with grain around breeding time, a method shepherds use to increase ovulation and produce more twins.
We are excited because we are getting the lambs we want for our breeding and wool program; two nice Moorit girls, one of whom, Espresso, is very dark. It has been a goal of mine to get some dark Moorits, as their fleeces tend to fade as the sheep age, much more than the black/grey fleeces do.
After a long run of singles, we got back into twins a few days ago, including this pair of ram lambs born to our 75% Cormo ewe, Sarina. Perry is their father, so the lambs are 88% Cormo, our highest percentage Cormo lambs yet. Cormo wool is very fine, and our Cormo-Corriedale crosses have lovely fleeces that make wonderful soft yarn.
We’ve also has some black & white pairs of twins that illustrate some fun genetic principles. In our Corriedale and Cormo sheep, the black color is dominant. So an individual will be black if they carry just one copy of the dominant black gene. Most of our black Corriedale/Cormo sheep do each have just one copy of the black gene, so when bred to a white mate, each of their lambs has a 50% chance of inheriting their copy of the dominant black gene and being black. Shadow is a Corriedale/Cormo -cross ewe, and she was bred to Princeling, a 75% Cormo ram, who is also black. So each of Shadow’s lambs had a 75% chance of being black and a 25% chance of being white. And she had one of each! A black boy and a white girl.
Shadow’s family nicely illustrates that, in breeds where the black color is dominant, you can breed a black ram to a black ewe and still. have the possibility of getting a white lamb!
But in those breeds where black is dominant, you would never get a black lamb from a ewe like Sarina, above, who was bred to a white ram, because you know with certainty that neither parent had the dominant black gene (or they would have been black), so there is no black gene for a lamb to inherit.
On the other hand, in our Romney sheep, the black color is due to a recessive gene. So a white ewe like Pip might carry a copy of the recessive color gene, but if she has only one copy, she will be white, because it takes two copies of a recessive gene for an individual to show the trait. White sheep like Pip, who we know have a copy of a recessive color gene, are called “B-factor” individuals. They have a copy of the color gene, but it is hiding behind their white color. Each of Pip’s lambs had a 50% chance of inheriting that hidden recessive color gene. If she were bred to a white B-factor ram, each lamb would have a 25% chance of inheriting the color gene from both parents and being black.
We don’t like to make those kinds of crosses, though, because the white lambs that come from those crosses may or may not be B-factor sheep, and we have no way of knowing, so we have kind of “lost” that recessive color gene.
Instead, we breed B-factor white Romneys to recessive-colored Romneys and then we know for sure what each lamb’s genotype is, because they always get a recessive-color gene from their recessive-colored parent.
In Pip’s case, she was bred to our recessive-colored ram Sky King, so her lambs for sure inherited a recessive color gene from their father. And in Pip’s case, one of her lambs got her recessive color gene, and was born black, and the other did not, and so is white. But we know that lamb is B-factor, because she must have received a recessive color gene from her father Sky King.
