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Avoid the Skin Biopsy Blues

July 16, 2009

bestBalbinaPicOkay, so Skin Biopsy testing has been going on in the U.S. for a few years now, what do we think of it?

EXPENSIVE ! …..I know about $300 per SB……….Im with you there.

The average alpaca scores around a 38 follicles sq/mm. An exceptionally dense alpaca has above 65 follicoles sq/mm.

Personally , we have not done any Skin Biopsy tests, but plan on biting the bullet soon and testing some of our herdsires, and a few of our important females.

What has convinced us to get the testing done?

We have several friends that have been getting these tests done regularly for the last few years, and they all seem to come away with the same surprising observations.

Since reviewing the scientific data of SB tests, most of our breeder friends conclude that

Human hands cannot accurately determine density of an alpaca.

What they once thought was dense is NOT, and what they thought was not dense is now very dense!

These particular breeders making this statement are very experienced breeders, all of whom have a minimum of 13 years in the industry, some are past AOBA judges. They claim that with the help of the SB test results, they are making significant changes in their breeding programs. One breeder had Stud A breeding most of his herd because he thought he was VERY dense (Stud A test was approx 45 fol/ Stud B was not used much because he was not dense. ( Stud B test results of approx 80 fol/sqmm), The 24 year alpaca breeder and past AOBA judge reversed his breeding males. He became a believer in the SB tests.

Other breeders are mentioning similar storys.

Okay, I can accept all of this. Technology triumphs again!

But this brings up another interesting point. If human hands cannot accurately determine density, why are we permitting judges to attempt such feats in the ring? Well, obviously we need to have judges attempt to figure out density in the ring, but what are the judges doing to catch up with this technology?

Hopefully some judges will comment.

My thought is that eventually, with the help of SB tests, experts will learn other visual fleece characteristics that correlate to high SB numbers………

I think that eventually, we all will all be capable of determining accurate density with the use of our eyes.

2 Comments leave one →
  1. July 18, 2009 4:57

    Don — there’s one thing about SB’s that people don’t talk about… the fact that it may not be a representative sample of the animals’ blanket. I have yet to find any studies that conclusively show that a skin biospy taken at a relatively random location on the animal’s body can be a true measure of that animal.

    How do we know that the area chosen for the SB wasn’t just unusually dense or not dense? Or for environmental reasons some of the folicles are dead?

    personally, I think a better statistical measure will be something that measures fleece weight per AFD/SD. In other words, which would you rather have:
    A. a stud who’s got 15 lbs of blanket at 22 micron, SD 4
    B. a stud who’s got 12 lbs of blanket at 18 micron, SD 6
    C. a stud who’s got 10 lbs of 20 micron, SD 3

    my preference would be C — most weight for the lowest/most consistent fleece.



  2. Marcee L. Stephenson permalink
    July 19, 2009 4:57


    You state that the SB is taking from a relatively random site on the alpaca. Skin biopsies are to be taken in a very specific spot on each alpaca tested.

    Wouldn’t the histogram’s from alpacas A, B, and C in your example above be taken from relatively random sites? Histograms from different sites on each alpaca could yield very different results.

    I think that the SB as well as the histogram are to be used as tools. The more tools you use, the more informed you are.

    Just my thoughts.


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