Reading Sheep Descriptions

Why I include what information I do with each sheep, and what it all means.

Under each sheep’s paragraph that I’ve listed in my flock, there is a set of data in a more quick reference form. For those who are unfamiliar with these data, I will explain what each means and why I included it.

AI Ancestors

First, there is the “AI Ancestors” heading. People have been importing semen from Iceland for some number of years now, in order to increase the diversity of lines in our American stock, and to improve the quality of the stock. A station called SouthRam houses the current rams whose semen is available. To learn more, visit SouthRam’s website.

The type of artificial insemination (AI) that is currently used is vaginal AI (VAI). I personally do not use AI, and am unsure if I ever will. I have several reasons for this. One, it’s costly compared to just purchasing a ram, and the ram has a much higher success rate. Two, the process, from my understanding, is simple, but the handling and temperatures of the semen straws are picky, and thus special training is needed to implement VAI. There are courses given throughout the US for those who do wish to learn, but I have never taken one as of yet. Three, there is a low success rate, and on a small farm, having even a few ewes not conceive is a lot of loss of productivity. And lastly, the sheep in Iceland are not exposed to our most dreaded and deadly parasite here in the United States: Haemonchus contortus, otherwise known as the barberpole worm. This means there is no selection for or against natural resistance to it. Thus it’s hard to know what will pass to the offspring; will they have some natural resistance to parasites or not? So I’d rather have sheep in my flock that have been bred to better survive on our American soil, or at least if they are a direct AI son or daughter, to have proven that they can compete with H. contortus. You can find more information about parasites in the Library, under the heading Parasites and their Control.

So while I do not use AI, I do find it a valuable tool to know what AI sires my sheep are descended from. The main reason for this is that SouthRam is very detailed about documenting the traits of each sire, and providing a picture. These data go above what can be found in the pedigrees, and I find them to be extremely useful when I’m researching the genetic history of my sheep. For example, if a ram is coded as “horned” in the pedigree, that just means that he has some form of horns, and not scurs. But it does not tell me what his horns looked like, which is a tool for helping to figure out if a ram has full homozygous horns, or heterozygous horns. I can look at what offspring he produced and get an idea, but this is still limited in use, and I’ve often wish I just had a good picture. SouthRam’s sire descriptions also give a quantifiable way of describing the traits of a sheep, which is far less relative than just saying, for instance, a sheep has good back muscling. What does that mean? SouthRam takes eye muscle measurements, which correspond to the thickness of the back muscle, and assign it a number of 1-5 for muscle shape. 5 is excellent, 1 is poor. It gives definition to saying that a sheep has good back muscling. I only wish that we in the United States had a way of quantifying our sheep like that. It would be so incredibly useful when making breeding decisions and studying pedigree.

So there’s my reasoning for why I would be curious to know the AI background of a sheep, and thus I included such information for those others who may also be curious.

Birth Size

This is simply if a sheep was born as a single, a twin, a triplet, etc. Birth size is often heritable, which is why I have included it. As in, if a ewe is born a twin, she is more likely to produce twins. The exception is the first birthing, which many times results in a single. A first birth is far less indicative of future birth size.

Lambing Record

For ewes, this shows how many times they have been bred, and how many lambs were born each time. If they were not bred or had no lambs a particular year, “n” is used. Sometimes a breeder will use “nb” to indicate the ewe was intentionally not bred. So a sheep that has a record of n112 did not birth lambs the first year she was fertile, her one winter year; had a single lamb her second year; a single her third year; and twins in her fourth breedable year. Just a note on the term “one winter”: A ewe is breedable before she turns a year old, the fall after she was born. (Around 6 months of age.) If she were bred, she would have only seen one winter at the birth of that lamb, thus the term “one winter ewe.” This is to avoid the confusing ewe lambs with one year old ewes that were bred their second fall as a yearling.

Genotype

This coding indicates the genes that are actually present within a sheep, seen and unseen. It shows all three loci that are present for color and pattern. See my article on Color Genetics in the Library for more information.

The first locus listed is the A locus, or the pattern locus. It can be one of the 6 following patterns:

Awt = White (Dominant to all other patterns.)
Agt = Grey-Mouflon Single Gene (Not confirmed in U.S.)
Ag = Grey (Codominant to Ab and At.)
Ab = Badgerface (Codominant to Ag and At.)
At = Mouflon (Codominant to Ag and Ab.)
Aa = Solid (Recessive to all.)

So an Awt sheep will always be white, no matter what the second pattern is that the sheep carries. Ag, Ab, and At are all equally dominant. So if any two of these are both present, both will equally express. Solid is recessive to all, and will only show if the sheep is AaAa.

The second locus is the B locus, or the basic color locus. It can either be moorit or black, as follows:

B = black (dominant)
b = moorit (recessive)

So a BB sheep is black and will only pass black, a Bb sheep is black, but carries moorit that can be passed to offspring, and a bb sheep is moorit and will always pass moorit.

The third locus is the S locus, or spotting locus. The sheep is either spotted or not, depending on whether or not they have two copies of the spotting gene.

S = Spotting Allele
s = Not Spotted Allele

So an SS sheep is spotted, and Ss sheep is not spotted but can passing a spotting allele, and an ss sheep is not spotted nor can it pass spotting.

Horn Code

This is used to indicate whether a sheep is horned or polled on a genotypic level, as in, what is in the genes rather than just what is seen. (See Horn Inheritance in the Library for more information.) I have used “p'” to indicate the presence of a horn allele, and “P” to indicate the presence of a polled allele. If a sheep is p’p’, then they are homozygous horned and will always pass a horned gene to their offspring. If they are Pp’, they can pass either to their offspring. PP will always pass a polled gene to their offspring. (Note: I do not have any sheep in my flock who are PP.)

p’p’ = Homozygous Horned
Pp’ = Heterozygous Horned
PP = Homozygous Polled