[Jacob-list] Jacob color genetics

[Neal and Louise Grose]

Fred and all,

This is a good and thoughtful survey of the connection between lilac coloration and breed. I would like to add some thoughts.

 I recall Dr. Sponenberg speaking about the origins of the Jacob breed. He indicated that it was highly likely that the Jacob sheep are a Viking breed. The predominant characteristics are of northern European ancestry. In 1985, Louise and I picked up a book in England entitled British Sheep Breeds published by the British Wool Marketing Board. This book states that the Jacob was imported from "the former Cape Colony". (I assumed that this is the Gibraltar area.) If I had to stake money on it, I would bet on Jacob sheep as horned, piebald isolates of the Viking type sheep, and that collected rams of similar appearance from the Mediterranean were added to these flocks.

I tend to think that it is most useful to think of 19th century "Jacob sheep" as a group of breedlets (maybe breeditoes). I recall from Ingrid's book Jacob Sheep in America that it was not uncommon for the Jacob breeders of that era to "not like the looks of" the other flocks. We may well have the most "purebred" Jacob sheep in history by virtue of intercrossing bloodlines and reselecting for consistent type.

Lilac coloration has cropped up in linebred sheep from at least four different bloodlines. There are variations in these colors, but I am not about to guess whether this is due to variants of 'lilac', reinforcement from various black genes, premature greying ...

Color perception can be tricky. There have been several references made to true black. Our B&W Jacob sheep are about the color of Heresy's dark chocolate. I do not recall seeing any sheep that would be the black of Holstein cows. We need to keep in mind that the physical properties of the wool fiber can also effect color, in much the same way as Mohair appears more white than do similar fibers. Our 'lilacs' are probably close in color to milk chocolate. These are actually "red" or yellow undertones and not gray. Various people that look at these sheep say that they see lavender undertones. I keep looking over Fred's letter, and nothing fits perfectly to explain lilac coloration. Based on what we have seen here, the black is there, but altered in the lilac sheep. I wonder if the 'lilac' allele is at a position that if expressed would knock out the non-yellow expression in the black. (This could be through a block of a precursor for the eumelanin.) Remember that one form of mutation is the simple repeating of a gene. Could 'black' gene be multiples of one of the lower browns? If I go to paint on the computer: start with an approximation of moorit and increase the 'red' and the 'lum', I get "black". Where's them art people when you need them...

One thing that I would like to caution about is the use of any one gene to make a determination of what is and is not purebred. We see sex-linked hornless here very occasionally. We started seeing this after 12 years of in-breeding. This is hornless only in females. I have back-bred one to her sire, she produces strongly horned male offspring. This is the 'Hornless' gene that is in Shetlands and several other northern European breeds. Yes, this may well be due to some crossbreeding 25 years ago, but it may just as well be the result of mixing flocks in the early 1800's before anyone gave a ...care about "Breeds". For my money, I will stick to things like rump structure, wool covering of body, hoof structure...  Now if we have a sheep presented that is hornless, 90% black and grayed out..I don't think so.

Neal Grose
  ----- Original Message ----- 
  From: Jacobflock at aol.com 
  To: honeybucket at bushwick.com ; patchworkfibers at alltel.net ; critterland at bendcable.com ; jacob-list at jacobsheep.com 
  Sent: Tuesday, May 06, 2003 11:21 PM
  Subject: [Jacob-list] Jacob color genetics


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