[Jacob-list] Crimp and micron counts

[Neal and Louise Grose]

Yes, I am referring to standard deviation within the sample from the shoulder area. (Double check me here Robin.)

And I should have said average fiber diameter (AFD). That is what I get for trying to think after getting up and milking cows at 3 and having company over and looking at stuff on email at nine while enjoying a cup of eggnog.

As it happens, the first micron test I could lay my hands on was from a semi-double coated Jacob.*  This one has a ADF of 30.5 microns and a SD of 9.5 and a coefficient of variation of 31.2%. In this sample, there are fewer fibers actually AT 30 microns than at 18 and 35. Normally, on a 30 micron fleece, more fibers should be at 30, with 60% of the fibers in a fairly small range  around that. 95% of the fibers should be within 2 SD of the mean. This forms a standard bell curve. The coefficient of variation in this sample should be much higher; that is, the curve should look more like a bell curve. +/- 2 SD here is a range of 38 microns, from 16 (Merino) to 54 (buffalo).

Our early efforts to compile micron tests in to a base for Jacob sheep did not take into account the change in ADF as the sheep aged. I suspect that Jacob sheep change more than standard breeds. This gave us large CV within the population. We were in effect looking at "double fleeces", overlapping bell curves of the flocks by comparing lambs to older animals. I will be very interested in seeing how the fiber study Gary and Co started comes out.

* OK, they are not SUPPOSED to have them...but some do. This particular fleece was from an adult ram who had coarsened considerably with age. His britch wool extended all the way to his hips. Let's keep in mind that crossbreeding will NOT give us double coated unless we are crossbreeding to a double-coated breed such as Navaho or Scottish Black Face. Having seen a Scottish BlackfaceX Jacob, I can tell you that the cross looks NOTHING like a Jacob. 

Neal
  ----- Original Message ----- 
  From: Linda 
  To: Neal and Louise Grose ; Betty Berlenbach ; Robin Lynde 
  Cc: jacob-list at jacobsheep.com 
  Sent: Wednesday, December 26, 2007 8:14 PM
  Subject: Re: [Jacob-list] Crimp and micron counts


  Just to clarify - when you say standard deviation, you are talking about the deviation within the lock/s sent to be micron tested, aren't you?   Not the deviation of the entire fleece from neck to britch?  What's a large standard deviation - in microns?  

  Linda
   
  www.patchworkfibers.com
  Registered Jacob Sheep, Angora Rabbits, Handspun Yarn



  > Betty and I have been round and round on this a couple of dozen
  > times. there are a few things to keep in mind, especially if you
  > are sending off samples for micron counting.
  >
  > Jacob sheep have crimp in the fleece, but shouldn't have defined
  > fleece crimp. The difference is that in order to have defined
  > fleece crimp, the fleece has to be rather uniform. That is, there
  > is very little variation within the fleece in micron diameter. A
  > Corriedale and a Jacob may well have the same Average Micron
  > Diameter, but the standard deviation figure in the micron count
  > should be greater for a Jacob's fleece. A coarse fleece may well
  > have a low std. dev. and have defined fleece crimp AND fell like
  > brillo.
  >
  > A fleece with TOO large a std.dev. is likely a double fleece. This
  > will show up in the graph of fibers from the sample as two
  > overlapped bell curves.
  >
  > If I had a preference, I would like to see us set a range for Std.
  > dev. if we set a range for AMD.
  >
  > Neal

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://www.pairlist.net/pipermail/jacob-list/attachments/20071227/2d48381e/attachment.html>