G-6-S . . . What do you know about it?    

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What is G-6-S and How is it Inherited?

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G6S is a simple recessive gene with a potentially powerful and deadly impact in the Nubian breed!

However, it can be removed (or bred out) in a short period of time (with careful selection and testing).

Referring to G6S and the Nubian genetics the following terminology applies:

AFFECTED - This animal has two copies of the gene and is (or may eventually be) symptomatic.

CARRIER - This animal only has one copy of the gene and is asymptomatic.

NORMAL - This animal has inherited two copies of the normal gene and is without symptoms (normal).

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While there are many more potential problems with an Affected animal, some of the following may be seen:

Generally immature or small for age, may appear to be stunted.

Muscular development may be incomplete, may appear unthrifty.

General health issues (and immune problems) may be higher than normal.

Underlying cardiac related problems may develop.

Fertility and reproduction may be compromised, and in some cases may not be functional.

Early death, with many not reaching beyond three or four years of age.

Various other physical symptoms which don't appear to have obvious reasons.

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The inheritance of the G6S is easily demonstrated by the following examples:

Using the terms above (Affected, Carrier, and Normal) we can demonstrate how G6S can be transferred (inherited) or totally avoided.  Each parent will contribute ONE of its two genes to the offspring.  What it has to pass along will depend on its own genetic makeup.

For this example we'll use "AG" for the affected G6S gene and "NG" to represent the normal gene.

(Keep in mind that the "AG" will trump the "NG" in any pairing)

NORMAL:  Has inherited both "NG" genes ... [ "NG" "NG" ]

(Both genes are normal, so we have a normal animal)

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CARRIER:  Has inherited one "NG" gene and one "AG" gene ... [ "NG" "AG" ]

(Remember, the "AG" gene trumps the "NG" and so this animal is a carrier)

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AFFECTED:  Has inherited both "AG" genes ... [ "AG" "AG" ]

(Since both genes are affected the result in an affected animal)

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What outcomes can there be from the above animals used in breeding programs?

Let's start with the NORMAL animals.

A Normal [ "NG" "NG" ] bred to another Normal [ "NG" "NG" ] can only produce Normal animals as there is no Affected "AG" to inherit in the offspring's pairing.  This is the safest way and most cost effective way.  Once you have Normal goats there should be no need to worry.

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The next scenario is a fairly simple math problem (probability) of offspring by using a Normal [ "NG" "NG" ] animal and breeding it with a Carrier [ "AG" "NG" ] animal.  Since the Normal parent can only contribute the "NG" gene it makes it very simple to figure out.  The variable is with the second parent which can contribute either its "NG" or its "AG" to the offspring.  This gives a 50/50 chance of the offspring being either Normal or a Carrier: [ "NG" "NG" ] or [ "AG" "NG ].  At this point it would be advisable to test the offspring as there is a 50% chance it may be a carrier.  Once a test or Normal is achieved the animal can be used with other Normal animals without worry.

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Now we get a little more complicated in using an Affected [ "AG" "AG" ] animal with a Carrier [ "NG" "AG ] animal.  Since the Affected parent can only contribute the "AG" to the offspring we are in a far greater risk of producing either more Carriers or more Affected animals depending on what the offspring inherit from the other parent.  The Carrier parent can contribute either the "AG" or the "NG" to the offspring.

The odds that the offspring may be Affected [ "AG" "AG" ] are 50%.  Likewise the odds that the offspring may be a Carrier [ "AG" "NG" ] are 50%.  There is no option for Normal [ "NG" "NG" ] resulting offspring when breeding an Affected with a Carrier.

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When a Carrier [ "AG" "NG" ] animal is bred with another Carrier [ "NG" "AG" ] animal the resulting offspring may fall into any of the three categories: Normal, Carrier, or Affected.  Since both parents are a Carrier [ "AG" "NG" ] there is a 50/50 chance they can contribute the "AG" or the "NG" to their offspring.  The same is true of the other parent.  So, in this example the resulting offspring may be 25% Affected [ "AG" "AG" ] animals, 25% Normal [ "NG" "NG" ] animals, or 50% may be Carrier [ "AG" "NG" ] animals.

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The final example is of breeding an Affected [ "AG" "AG" ] animal with another Affected [ "AG" "AG" ] animal.  Since there are only "AG" genes to contribute from either parent the resulting offspring may be 100% Affected [ "AG" "AG" ] animals.

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How to use G-6-S Testing as a Breeding Tool:

In the above scenarios the status of the animals are known.  However, the reality is that very very few animals being used in Nubian herds today are tested.  Without testing the "AG" can be carried forward generation after generation without even knowing it until one day you have a kid that just doesn't quite grow right.  It may be slow, a bit dumpy or puny, or it may not even show any signs until a few years later.  Then for "unknown reasons" it dies an early death.  It may not even die, it may just become unthrifty, become overlooked as an animal that just isn't a "good doer," and no more thought given.  You may have already bred with this animal, contributing more of its genes to your program.  Another option is you may have nice growthy kids, they all look well, do well and act just fine.  Remember, that even a "Carrier" goat will appear, grow, and act normal.  This appearance of normal can still be carrying (and passing on) the "AG" gene down to its future offspring.

How then do we fix this?  Can we fix this?  The answer is with testing, information, and sharing of that information.  We are in one of the greatest times in our history.  We have countless tools available to us.  We can share information vastly and expediently with the internet, e-mail, websites, etc.

Only once the stigma (and unrational fear) of G6S is brought into check by Nubian Breeders will there be an opportunity for real progress and potential to eradicate (yes ERADICATE) this gene from our beautiful Nubian breed!  Eradicate is a very strong word--and it IS possible.  However, human nature being what it is, most likely it is not probable.

But... There is hope.  Knowing the G-6-S status of your animal can give you a very powerful tool.  Remember, once you are working with a known "Normal" [ "NG" "NG" ] animal you have nothing to consider if you breed it with another "Normal" [ "NG" "NG" ] animal.  Your resulting offspring can all be 100% normal (by inheritance).

Again, if tested animals are utilized even "Carrier" animals can work into your breeding program.  There is no reason to consider throwing out the baby with the bathwater.  If there is a great genetic powerhouse of a buck you wish to use, and if he is a Carrier, so what!  Test the doe you wish to breed him to.  Know what your odds are before you make a great breeding decision and find out the hard way (the way of genetic inheritance) that there is a problem.

If you breed a Normal animal and a Carrier, it is easy enough to test an offspring and see if it has inherited the gene.  Remember, once you achieve a Normal animal you are back in the freeway of your genetics program.  It is not a shame for any animal to be a "Carrier" ... that is simply part of what is in the makeup of our beautiful Nubian breed -- we can embrace this issue, stand up and look it square in the eye, and test to be sure.

Knowledge is power -- we have all heard that -- it's time to get Powerful and pull our heads out of the dark ages.  G-6-S is something that can be totally managed--easily!

I have had people ask about the worries of CAE and CL in comparison to G-6-S ... and the only thing I can say is this: "If you could fix it forever, would you?" ... with Testing it can be done!

The next move is up to you -- the Modern Nubian Breeders of Today!

  ~Bill.

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             - Related Informational Links on G6S -              

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"G-6-S: A Genetic Defect and its Management"

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"Another Look At G6S"

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One Breeder's View on G6S and their Herd's Story:

The BMR G6S History

(posted with permission)

     When we went from having home milkers to having a commercial cheese dairy,

it suddenly dawned on me what a big responsibility it can be to breed goats.

Good conformation and high production are important for our operation, but

health tops my list every time. Sick goats aren't as productive and take up

way too much time. Then another breeder called me up to tell me that she had

just spent almost $1000 in tests on her herd as she tried to track down what

was wrong with one of her does. The doe's symptoms sounded like classic G6S

Affected symptoms. Unfortunately the doe had been destroyed by then so it

was too late to test. That's when I decided that G6S was an important

health AND economic consideration.

     As the cost to test our entire herd was pretty high, I decided to just test

all of our bucks. Four out of five tested as carriers! The carriers were

banded. Thank goodness for Reuel Rhesa's JJ Rio Grande who had been flown

down from Sandy Riehle's place in WA earlier that year. He was the only

Normal boy (and is still the shining star of my buck herd). Debbie Emholtz

of Jacob's Pride, bless her heart, also came to my rescue and lent me a

lovely G6S normal buck to use. Another friend lent me a very nice (very

expensive) fella from a nationally known herd, but he turned out to be a

Carrier. We used him on two does - all his kids tested as Carriers.

      Since there had been so many carriers in my buck population, I was quite

worried about the does. Most of the bucks were youngsters that I had kept

or purchased due to my growing commercial herd needs and hadn't used yet,

but I was still worried. So I took the plunge and tested everyone. I was

very relieved that only three of the does tested as carriers. This all

happened in 2005 - can you imagine what a herd full of G6S affected animals

I could have now? It cost over $2000 to get the herd tested but I am SO

thankful that I tested that year. By now I would be losing a lot more money

than that due to dying kids. It still took me 4 more years to finally have

a fully G6S Normal herd since my Carrier does were quality enough to

continue working with.

     To offset my costs I added a $50 surcharge onto each kid that I sold. The

G6S testing "investment" was easily repaid in less than two years. In

fact, I found that people were so anxious to get G6S normal goats that I

have been able to raise prices even higher - and still get people from

across the country coming here to pick them up. I don't look at testing as

an expense - it truly is an investment. Between doing LA, DHIR, CAE

testing, being CL free, and G6S normal, my kid prices are almost triple what

they were 5 years ago. In effect, my testing creates more income - as well

as helping me produce goats that I can be proud of.

     Some people have been wondering how prevalent G6S is. Whether the

statistical "averages" are 1% or 99% for me it just doesn't matter. I had a

G6S time bomb in my herd and I'm glad that it got defused. Is it a worse

"disease" than CAE? That's a specious argument. Every owner/manager has to

make that decision for themselves. Having the information from which to

make the decision is the important thing. Simply discussing this issue sure

doesn't take away any of the importance of fighting the other problems that

crop up in our herds.

     Anyway, this is what happened here at Black Mesa Ranch. Best of luck to

everyone with their herds. Happy New Year.

Kathryn Heininger

Black Mesa Ranch

Snowflake, AZ

Come see us online at:

http://www.blackmesaranch.com/

Where do I have G6S Testing Done?

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   Texas Veterinary Medical Diagnostic Laboratory  - TVMDL  

College Station Laboratory

PO Box Drawer 3040

College Station, TX 77841-3040

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Phone (979) 845-3414,

Toll Free (888) 646-5623

Fax (979) 845-1794

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Please visit their website:

http://tvmdlweb.tamu.edu/

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*** TESTING is a ONE TIME EVENT - An animal's status doesn't change! ***