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Baa Baa Brown Sheep….

By Wendy Allison, Wairarapa

In the last article we looked at how the alleles your sheep has on the Agouti locus affect how much white it will have on it, whether it’s all white, white markings on colour, or all coloured. But, if you remember in the first article we mentioned there are three main loci (places on the DNA) that affect colour.

White lamb showing black nose and eyeliner
Urchin showing you her black nose and eyeliner

The second locus we’re interested in is called Brown, and it determines what colour your sheep’s skin will be. There are only 2 options – black or brown – hence the name. Most sheep have black skin because black is dominant. Even white sheep, if you look at the bare part of their nose, their hooves, and around their eyes, usually have black skin.

Brown Sheep

However, some sheep have brown skin, hair, and wool. This is often called moorit.

Brown in sheep is caused by a mutation that causes breakdown of a protective chemical called eumelanin in the sheep’s skin cells, causing the skin and any hair or wool that grows out of it to be brown.

Brown skin is recessive to black skin. If you remember in the first article with the punnett squares, we showed how different dominant/recessive alleles might affect the colour of a lamb. It’s the same for black skin and brown skin. So, a lamb needs both the alleles on the Brown locus to be brown before the lamb will be brown. Any animal that only has one brown allele will have black skin – but could pass on the brown allele to their lambs.

Black skinned ewe with one brown and one black lamb
Luci has black skin but carries a brown allele so she is able to have a brown lamb. The lamb must have inherited a brown allele from her sire as well, but her twin brother didn’t so he came out black
Black skinned ram
This is Nero, the sire. He is not brown, but carries a brown allele. His one and Luci’s one combined to create a brown lamb

Neither of the parents of the pictured brown lamb are brown themselves – Luci is self-patterned and Nero is light blue, and they both have black noses, feet, and eyeliner. While their wool has faded to brownish, it’s black on their legs and at the skin whereas the newborn lamb is obviously brown.

Brown skinned lamb

In this pic you can clearly see that the skin on her nose is brown, not black

Brown lamb's fleece
Muppet’s lamb fleece, showing that the brown wool goes all the way to the skin

in the close-up of Muppet as a lamb you can also see she has a white nose ring and a little moustache. This shows she has inherited the blue pattern on Agouti from her sire. If you remember, this is dominant to Luci’s self pattern. So we know that Muppet is a brown sheep with a blue pattern. Her wool will fade as she ages, but she’ll always be brown because it’s in her genes. NB: a sheep with two brown alleles on Brown that also has dominant white on Agouti will have brown skin but the wool will be white.

Muppet with her first lambs
Muppet as an adult with her first lambs. The ram had black skin and was self-patterned. Both her lambs are black because they only have one brown allele, but her blue pattern has come out to varying degrees on both of them.

Muppet would have to be bred to another brown sheep or one carrying the recessive brown allele to get brown lambs. But, her lambs are both carrying one brown allele so they could produce brown lambs with the right mating. Another reason for keeping good records!

Three different coloured lambs
All of these lambs have the same sire!

In the next article, we’ll look at spots, and explain why brown spotted sheep are quite rare.

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