With the new year well underway, members of…
By Wendy Allison, Wairarapa
In a previous posting ‘Genetics – How do we get coloured sheep’, we looked at how the alleles that a lamb inherits from its parents, on the place on its DNA called Agouti, govern whether it will be white or coloured. The example we used, Stumpy’s lamb, was not completely black. He’s got a grey saddle over his back and some white bits around his face. In this article we’ll look at how you get patterns like this on sheep.
The coloured or white wool that you see on your sheep is actually a colour pattern, and it’s controlled by the alleles we discussed last time that make it white or coloured. So if a sheep has the dominant white allele on Agouti, the pattern will be ‘all white’. If the sheep has two recessive colour alleles on Agouti, the sheep will be coloured. Just like the punnett squares from the last article.
But it’s not just black and white – there are a few different recessive colour alleles, and some of them can cause black sheep like Young Joel to have a colour pattern with white (or sometimes tan) hair and wool mixed in with the black. This is called a white display.
Basically, colour pattern in sheep is a spectrum, with completely white – called white/tan – at one end, and completely coloured – called self – at the other. All coloured sheep have the recessive coloured alleles, but how much colour they have depends on which ones they get.
All hairs and wool white(white/tan)
Various patterns of white hairs/wool among the colour
All hairs and wool coloured(self)
The ‘white is dominant and colour is recessive’ rule still applies, and a fully coloured sheep with no white hair or wool is the most recessive combination. In between these are varous patterns of white markings. These patterns have varying levels of co-dominance. Co-dominance is where no pattern is dominant so both patterns show up in different ways , and it can lead to some interesting markings.
A number of different patterns expressed at the Agouti allele have been described and given names, some of which are reasonably intuitive (eg ‘self-patterned’, ‘light badgerface’ and ‘lateral stripe’) while others are less obvious (eg ‘blue’, English blue’).
A few examples of the Agouti pattern spectrum from our flock, mostly variations on ‘blue’
Nero is light blue – he has a white ring around his nose, white teardrops, white ‘fangs’, and a very light saddle over his back.
Jimmy is English blue – he has teardrops, a white moustache, white frosting on his ears, and a lighter saddle but is much darker in general than Nero. Jimmy is from a light blue ram over a self (all black) coloured ewe.
Jess is Paddington blue. If you look closely you can see he has a tiny dot of white on his forehead, and he also has white spots just under his ears. Otherwise he’s completely black. He is from a self-patterned ram over a light blue ewe.
Lumpy is self-patterned, she has no white on her at all. Both of her parents are self patterned. She will fade to grey over her back as she ages but she will not have white displays.
Combining different colour-patterned parents can have unpredictable results, and with co-dominance you can get two patterns displaying together. Looking back to Young Joel, he is by a self-patterned ram from a white ewe whose father was light blue. He seems to have inherited the blue pattern from his grandfather through his mother’s recessive black gene – he has teardrops and a moustache but he doesn’t have fangs or a full nose ring so he’s not a true light blue. He is a mix of colour patterns.
There are many other patterns on Agouti that we haven’t covered here, and new patterns and their genetics are being found and recorded regularly. Working out what patterns your own sheep have is part of the fun of breeding coloured sheep!
The American Romney Breeders Association’s website includes some descriptions of colour patterns for Romneys: ‘Patterns in sheep – the Agouti locus’ . There is also a very good article covering patterns on other breeds by Roger Lundie in the book ‘The World of Coloured Sheep‘. If you don’t have a copy of that excellent book (now out of print) you can download the pdf from the BCSBA’s website.
In our next article we’ll look at how you get brown sheep .