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Offline aj

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Re: New genetic defect in Angus ?
« Reply #45 on: January 15, 2012, 11:02:45 PM »
Is this defect mentioned in the "Angus Journal" or their web site.
People can't believe we have such a big moon for such a small town.

Offline knabe

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Re: New genetic defect in Angus ?
« Reply #46 on: January 15, 2012, 11:05:48 PM »
Trev......Jeeez......they can't put pictures of shorthorns on here.......its a angus thread........"The business breed".

When did they drop the "defect free breed" marketing campaign.
Im offended by liberalism, can I sue the DNC to ban it?

Offline CAB

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Re: New genetic defect in Angus ?
« Reply #47 on: January 16, 2012, 09:24:37 AM »
It'll be interesting to see the results of the testing for this potential defect, but as far as the picture posted up possibly representing the defect, I think that most of the older members here on the planet have seen very similar pictures of or even live individuals that are actually a pair of conjoined twins calves in which one of the calves survived and along the way absorbed the other calf which ended up expressing itself as a 5 legged calf or a 2 headed calf or on & on.


CAB - this defect is not the same as extra limbs resulting from co joined twins - the anatomy is different and there appear to be a line of cattle affected - just like the potential genetic defect in shorthorn cattle we need samples and pictures and pedigrees


So Lana is this how this new possible defect expresses itself, or do you think that this looks more like a pair of twins that were joined while in the womb?

Offline DL

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Re: New genetic defect in Angus ?
« Reply #48 on: January 16, 2012, 04:30:51 PM »
It'll be interesting to see the results of the testing for this potential defect, but as far as the picture posted up possibly representing the defect, I think that most of the older members here on the planet have seen very similar pictures of or even live individuals that are actually a pair of conjoined twins calves in which one of the calves survived and along the way absorbed the other calf which ended up expressing itself as a 5 legged calf or a 2 headed calf or on & on.


CAB - this defect is not the same as extra limbs resulting from co joined twins - the anatomy is different and there appear to be a line of cattle affected - just like the potential genetic defect in shorthorn cattle we need samples and pictures and pedigrees



So Lana is this how this new possible defect expresses itself, or do you think that this looks more like a pair of twins that were joined while in the womb?
 

No CAB - it is different - while polymelia is also seen in improperly divided twins (eg. ischiopagus conjoined twins where one twin is acephalic and parasitic) but this is a bit different to notomelia.Notomelia (description below) is not just polymelia -see site below for pictures

information from Australian vet doing the work (L Dehnholm)

http://s107.photobucket.com/albums/m298/denholml/Polymelia%20in%20Angus%20calves/

SUSPECTED HERITABLE NOTOMELIA IN ANGUS CALVES

At least 15 cases of notomelia have been reported in Australia in the last two years, all in Angus calves. The majority of these notomelia cases were reported from a single purebred Angus herd which has been linebreeding to high carcase value American Angus AI sires such as BRND 036 and CA Future Direction. Other recent notomelia cases here were sporadic and scattered across Angus herds all over South-Eastern Australia and Western Australia, but where pedigree information has been available in these sporadic cases it points to a similar genetic background in those cases to that of the cases in the main affected herd.

Several polymelia cases have been reported recently in the press and even on TV here in Australia (See http://www.geelongadvertiser.com.au/article/2009/08/14/93641_news.html and http://au.news.yahoo.com/thewest/a/-/offbeat/7017620/five-legged-calf-surprises-farmers/). All these cases were Angus calves, although one case reported in the New Zealand press was a Holstein calf.

Notomelia is a form of polymelia ("many limbs") in which the affected child or animal is born with supernumerary limbs (ie. limbs above the normal number of limbs for the species). In the case of notomelia, the additional limbs are attached to the site of the embryonic notochord. In the developing embryo, the notochord defines the long axis of the body and the development of the body segments (somites). In the normal embryo, limb buds occur in many of these embryonic segments that form adjacent to the notochord, but in mammalian embryos all but two of these limb buds on each side of the body regress during the early patterning of the body so that mammals have only four limbs. In polymelia, it appears that this normal process of limb bud regression fails and extra limbs result from continued growth of the supernumerary limb buds that degenerate in the normal embryo.

The genetic control of supernumerary limb bud regression in mammalian embryos is not well understood to date, but supernumerary limbs occur in Drosophila spp fruit flies as a result of loss of function mutations in the gene slimb. Slimb is known to be involved in the proteosomal ubiquitination process that leads to inhibition of entry to the nucleus and then intracellular degradation of certain proteins required for the transcription of genes involved in controlling the cell cycle (ie cell replication). Without the slimb protein, the normal programmed death of cells in the supernumerary limb buds in Drosophila apparently fails and extra legs result. However, slimb is just one of many genes involved in these complex pathways controlling cell replication during body patterning.

The slimb gene is very well conserved in an evolutionary sense and a homolog called beta-TrCP is present in man and expressed in certain tumours, although its functions in mammalian embryonic development are unknown. Nonetheless, the Drosophila genetics demonstrate a potential molecular basis to polymelia in mammals including calves and beta-TrCP is known to be involved in similar biochemical pathways in mammals to those in which it is involved in Drosophila.

Although I want to stress that there is no proof yet that notomelia is a heritable disorder in the Angus breed, the field evidence cited above is strongly suggestive of this. DNA samples have been collected from a number of cases and affected calves have been retained for a trial breeding program. The research approach that I intend to adopt with these notomelia cases will be similar to that which I used for CA (contractural arachnodactly).

The mortality in notomelia affected calves is high (approx 50%) due to dystocia. A number of cases have required fetotomy to deliver the calf. Surgery to amputate the additional limbs from surviving notomelic calves can be simple or very complex, depending on the anatomy of the limb attachment.

Last Thursday I watched a surgical procedure where two veterinary surgeons took more than an hour to remove the extra legs from one notomelic calf.

Although the notomelic defect is not uniformly lethal like AM and NH, the cost from dystocia, dead calves and occasional dead mother cows, plus the cost of amputations in the survivors, is quite significant.

If this proves to be a recessive disorder in Angus calves I believe it will be just as significant as any of the other defects we have faced in recent years.

I am very interested in obtaining DNA from further cases of notomelia in newborn Angus calves and I would appreciate hearing from anyone who learns of a notomelia case where at least some pedigree information is available and DNA can be obtained from the calf and its mother, and preferably also from the calf's sire.

I have loaded a number of photographs of these notomelia cases onto my Photobucket site.

See http://s107.photobucket.com/albums/m298/denholml/Polymelia%20in%20Angus%20calves/.

Dr Laurence Denholm


Going to church doesn't make you a christian any more than standing in a garage makes you a car

Offline Aussie

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Re: New genetic defect in Angus ?
« Reply #49 on: January 16, 2012, 11:46:19 PM »
Thanks DL (thumbsup)

 

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