Dexters - Learned a Lot Today

Discussion in 'Cattle' started by YuccaFlatsRanch, Jan 1, 2007.

  1. YuccaFlatsRanch

    YuccaFlatsRanch Well-Known Member Supporter

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    Learned a lot about Dexters today - some of which is scary.

    1. Dexters can carry the Bulldog gene which is a recessive gene that when expressed causes calfs to be aborted and born with virtually no bone structure. I.E. only buy Bulldog free tested stock.

    2. Come mainly in black (least expensive), Dun (next least expensive), Red (very expensive).

    3. Come polled and horned. Polled more expensive.

    Therefore a polled homozygous red heifer is the most expensive - in the neighborhood of $2K at 90 days old.
     
  2. ~Tomboy~

    ~Tomboy~ Well-Known Member

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    Hi Yucca,

    In Dexters the Chondrodysplasia (bulldog) gene is NOT recessive. It is a dominant gene.

    Mating a carrier bull to a carrier female has a 25% probability of producing a bulldog calf, a 50% probability of producing a carrier calf and a 25% of producing a non-carrier calf. Mating a carrier of either sex to a non-carrier of the opposite sex has a 50% probability of producing either a carrier calf but no chance of a bulldog calf. Mating two non-carriers produces only non-carriers calves: no carrier or bulldog calves.

    IF you can find a homozygous polled red heifer for 2K I would say that's a great price, if the heifer was heterozygous polled that would be more in line.
     

  3. ~Tomboy~

    ~Tomboy~ Well-Known Member

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    OK need to back track some.

    The last heterozygous polled red heifer I knew of that was sold went for 3K.
    Their numbers are very few probably less than 75 animals.

    As far as a homozygous polled red heifer, I personally don't know of any, my guess would be less than a handful.

    Hope this helps.
     
  4. YuccaFlatsRanch

    YuccaFlatsRanch Well-Known Member Supporter

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    Barbara - what you described in your genetics example is classic recessive gene expression. Its the same as blue vs brown eyes in humans. Brown eyed male who carries recessive blue mated to brown eyed female who has recessive blue gives 25% brown eyed with no recessive, 50% browned eyed with recessive blue, and 25% blue eyed double recessive. If bulldog was dominant the heterozygous animals would all die from the dominant expression of the gene same as the homozygous carriers do.

    And although I am wrong about the actual cost of a homozygous (homozygous negative bulldog) polled red heifer, they still would be the most expensive.

    I personnaly couldn't care less about the color, but I sure am not interested in any with the bulldog gene. Any I would consider buying would have to have been tested or come from two certified bulldog gene free parents.

    BTW - I spoke to a friend of yours today in Comfort, TX today about buying a cow or heifer later in the year.
     
  5. Slev

    Slev Well-Known Member Supporter

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    I already know a lot about Dexters, and I'm quite happy with mine. Always room to learn a little more though.... (someday I'd like to get a Jersey just so I can compare)
     
  6. Nyx

    Nyx Misplaced Appalachian

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    The bulldog gene is dominant. But it isn't lethal unless the calf has two copies of it. Heterozygous carriers show the trait (evidenced in shortened leg bones and a more muscular build) meaning the trait is dominant. Recessive traits need two copies before they show. Mating two heterozygous for the bulldog gene gives a chance for a bulldog calf that has the lethal two copies. Mating a heterozygous with a normal (not having the bulldog gene) Dexter means there is no chance of a bulldog calf.
     
  7. genebo

    genebo Well-Known Member Supporter

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    Perhaps the term "bulldog gene" is throwing you. In fact, the chondrodysplasia gene that we're talking about is a dominant gene that causes dwarfism. When a single gene is present, you will always get dwarfing, as evidenced by shorter legs. While this is dominant, it is never fatal. Cattle with this form of dwarfism are simply short.

    When a calf (or fetus) receives a double dose of the gene, it fails to develop properly and either aborts early or is stillborn. There are no cattle alive that have two of these genes. All living Dexters that carry a single copy of the gene are dwarves. It is only by mating two of these carrier cattle that you can pass on two copies of the gene to the fetus. All other mating combinations will pass on either none or one copy of the gene, so can not produce a bulldog calf.

    You have the right idea in wanting all your Dexters to be tested for the presence of the gene. That will give you 100% peace of mind about never having a bulldog calf, since parents that don't carry the gene can't pass it on.

    Many of us love the little dwarf Dexters and choose to keep them. However, I only keep a male dwarf. All of my females are non-carriers. Therefore, I will never have a bulldog calf. I may have some more dwarves, though, and that is very fine.

    Genebo
    Paradise Farm
    Church Road, VA
     
  8. ~Tomboy~

    ~Tomboy~ Well-Known Member

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    Chondrodysplasia is a large word, and can be very confusing when first learning about Dexters.

    Once you identify (test) you animals to see if they are carriers or not it is really very simple. Thanks Genebo and the rest for explaining it better than I could.

    We all have different ways of handling the gene. I have chosen to have my whole herd tested and they are all non-carriers. That means I will never have to test any of their offspring.

    Ah, you spoke to Mickey, she is a great person, I'm sure she'll treat you right.
     
  9. YuccaFlatsRanch

    YuccaFlatsRanch Well-Known Member Supporter

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    Yes I spoke to Mickey and we are going to see her animals this next weekend.

    My college minor was in genetics and whatever people want to call the "bulldog gene" - I want no part of it. I NEVER allow major faults to be bred into any of mine stock - at least knowingly.

    It is good for people to know about the Bulldog gene because as Mickey indicated - not everyone is willing to either talk about it in their herd, and even less seem to be willing to test for it.
     
  10. Carol K

    Carol K Well-Known Member

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    YFR,
    I hope we can welcome you to the wonderful world of Dexters soon then!
    You have a great bunch of people in Texas, they will help you out. See if you can set time aside to come to Colorado in June for our AGM and show, it will be a good one.

    Carol
     
  11. YuccaFlatsRanch

    YuccaFlatsRanch Well-Known Member Supporter

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    I will change from Beefmasters to Dexters soon - that is not a question. I have to wait until my cow has her calf in late February and wean it in June to sell her.

    I will however be VERY CAREFUL who I get one from and it will not have the bulldog gene whatsoever. Of coourse that is how I buy all of my stock. You cannot ever go wrong in getting the best quality when beginning a new herd/flock. Superior foundation stock is the only way to go even if you don't plan on raising very many of a type of critter. The way I figure it is I can raise twice as many Dexters as I can Beefmasters and unfortunatly that will be 2 cows with calves. The calves will be either for selling or for my own meat or sell one and eat one (the boys better watch out).

    I figure I can home butcher a 600 lb animal. That would be a 375 lb hanging carcass and that in 185 lb halves is manageable for my neighbor and I. A 1200 lb beefmaster steer is a bit more than we want to handle.
     
  12. Carol K

    Carol K Well-Known Member

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    YFR,
    I too have tested all my animals and have a Chondro. free herd.

    Carol
     
  13. ~Tomboy~

    ~Tomboy~ Well-Known Member

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    I couldn't agree with you more.

    Dexters will also be at The Houston Livestock Show and Rodeo again this year in March. Wish I could make it but it's smack in the middle of calving time.

    If you can't make it to Houston or Colorado, there is the 2008 AGM in TEXAS :hobbyhors .
    I'm planning for that one now.
     
  14. Terry W

    Terry W Duchess of Cynicism

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    Something you folks are missing out on when relaying the 25%/50%/25% ratios of free/carrier/affected.... That is ONLY a mathematical formula for predicting the possibility of what MAY happen when breeding carrier to carrier-- it is NOT what happens in the REAL WORLD....

    There is NO SUCH THING as a simple recessive-- that has been proven and verified. If you like a solid black bull, and he is "clear" that does NOT mean he is not carrying an allele that may help future generations express the undesired characteristics if/when he is bred to a carrier cow. The prepotency of an animal may or may not mask characteristics for generations, then someone may do what they thought was a well researched breeding, and wind up trying to lay the blame for a 'mishap' on the owner of a sire or the breeder of their female. when what really happened was Nature. I find it laughable that so many breeders 9 of any animal) state they have perfected the "art" when their products do well, then call breeding a 'crapshoot" when the results are poor. They refuse to acknowledge that there is a force bigger than all of us, that can throw a major wrench into our plans. That force is not going to follow a man-made chart designed to predict the POTENTIAL POSSIBILTY of an occurance, even though that chart was developed after years of recordkeeping.
     
  15. Carol K

    Carol K Well-Known Member

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    Terry W,
    the Chondro gene in Dexters is Dominant. A tested clear bull is just that, a tested clear bull.

    Carol
     
  16. genebo

    genebo Well-Known Member Supporter

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    Terry W,

    You have given a good picture of what happens with a recessive gene. However, the chondro gene in Dexters is dominant. As Carol K said, if a Dexter is tested to be free of the gene, then there is zero chance of that gene being passed on to that Detxer's progeny, unless it comes from the other partner in the breeding, who is a carrier of the gene.

    I'll repeat what I've said before: the chondro gene is not a stealth gene. It shows it's presence in the shape of the animals who carry it. That's where the short legged dwarf Dexters come from. The long legged non-carrier Dexters do not carry the gene in any form and can't pass it on. Ever. DNA testing will tell about those Dexters who defy the stereotypes and can't be positively identified by sight.

    Here's the odds:

    Mating a non-carrier to a non-carrier gives a zero chance of producing a carrier calf. No ifs ands or buts.

    Mating a non-carrier to a carrier gives a 50% chance of producing a non-carrier calf that is totally free of the gene and can never pass it on. The other 50% chance will produce a dwarf carrier calf, with one copy of the gene and the possibilty of passing it on.

    Mating a carrier to a carrier gives a 25% chance of producing a non-carrier calf that is totally free of the gene and can never pass it along. Another 50% chance will produce a carrier calf with one copy of the gene and the chance of passing it along. The final 25% chance will produce an embryo with two copies of the gene. This embryo will abort early or be born dead. This is the infamous "bulldog calf".

    Obviously, no one needs to ever have a bulldog calf. The reason that some were born in the past is that no one knew exactly how the gene worked until an Australian study defined it. The only reason that a bulldog calf might occur today is that someone might not be informed or else choose to take that chance because they so love the little dwarf carrier Dexters.

    I like the dwarf Dexters, but won't chance the bulldog calf. Therefore, I only keep long legged non-dwarf females. Many people have opted to only keep long legged non-carriers of both sexes, so for them, this whole issue is meaningless. They will never breed a dwarf carrier calf.

    Genebo
    Paradise Farm
     
  17. ~Tomboy~

    ~Tomboy~ Well-Known Member

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    Genebo, Very well said.

    I was looking for one of those applauding smiley faces to use, just didn't see it.
     
  18. genebo

    genebo Well-Known Member Supporter

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    Barbara,

    Thank you, but I made a mistake when I originally posted. I had the odds wrong for non-carrier to carrier. I edited the post to correct it.

    Out of 11 births from my carrier bulls over my non-carrier cows, I've had 7 non-carrier calves and 4 carriers. I believe that the difference between my luck and 50/50 is that the carrier semen is not as likely to fertilize. That and the possibility that an egg fertilized by carrier semen may not implant. The result here being that it takes another cycle before the cow is bred, and it isn't noticed.

    Genebo
    Paradise Farm
     
  19. YuccaFlatsRanch

    YuccaFlatsRanch Well-Known Member Supporter

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    "Obviously, no one needs to ever have a bulldog calf. The reason that some were born in the past is that no one knew exactly how the gene worked until an Australian study defined it. The only reason that a bulldog calf might occur today is that someone might not be informed or else choose to take that chance because they so love the little dwarf carrier Dexters."

    AND UNFORTUNATELY as a breed becomes popular less importance is usually placed on purging the herd of "defective" animals. The almighty dollars wins far too frequently. In each of the forums you occasionally hear about Linebreeding vs Inbreeding. They are essentially the same - you can get some spectacular animals this way as you double up the positive genes. You can also get some disasters genetically. The SECRET is not in which animals you keep, but in ensuring you KILL or neuter ALL but the extraordinary animals. Money however gets in the way of doing this - look at dogs and AKC - its amazing how many good breeds of dogs have become popular and subsequently become garbage due to selling of inferior animals.

    It is possible to eliminate the Bulldog gene totally from the Dexter breed, but doing so would severly impact the numbers of the animals available. TOO MANY BREEDERS just don't care.

    I will only have Bulldog free Dexters when I decide to purchase one.
     
  20. Terry W

    Terry W Duchess of Cynicism

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    Genebo-- EVERYTHING is polygenetic-- Just because ONE LOCUS is not showing up in a test, does NOT mean the animal is not hiding factors, yet unidentified, that contribute to the expression later on down the line.. ALWAYS breed expecting something "odd" to crop up--Even from "tested clear" animals.
    YFL-- A GOOD breeding program Does not abse itself on the across the board refusal to use something that may not be perfect. It is the imperfections that provide for genetic diversity to remain, and keep the overall population healthy.

    I can't help it that I am a Diversity freak. A well respected geneticist died recently--he was my uncle--AS far as the AKC and registered dogs go-- it is the elimination of "flaws" that lead to the shrinking gene pools and health issues. I know too much about what has gone on in THAT venue--Color genetics can and do affect sensory genetics. They affect nervousesystem genetics, as well.

    Just because a gene is ALWAYS Dominant does not mean several unknowns are not important in the expression of that gene.. THAT is what I am trying to tell you-- Just because you see no carrots in the soup, does not mean there were none used in the stock.....