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Posted: Sun Jul 25, 2010 8:47 pm
by dizzydex
Hi I wondered if I could ask for some clarification on the Chonrodysplasia test. Is the result shown in the herd book/pedigree. I want to look up some information on a certain line but could not find test results
Posted: Tue Jul 27, 2010 7:50 am
by Saffy
Well it isn't something I know much about but I don't think the test has been used that widely or around for that long to be easy to look up far down any line. Have you tried ringing and speaking to the DCS office as that is the best place for any questions like this. They will be able to answer you I am sure.
I have 14 registered Dexters and only one has had the test. That was because the person I bought her off hadn't got around to registering and then did it to sell when she was a couple of years old. It wasn't done just for chondo in her case - but for the DNA to prove parentage.
Stephanie
Edited By Saffy on 1280213701
Posted: Tue Jul 27, 2010 10:54 am
by dizzydex
Hi Stephanie, thank you for your reply, I was aware of the DNA element but had not thought about the fact that this would also prove the parentage.
I will ring the Dexter Society today and then show all the reply as I am sure it would help someone else in the future
Posted: Tue Jul 27, 2010 11:06 am
by dizzydex
Hi I telephoned the Dexter Society and Sue was extreemly helpful.
The information is not held in the herd book as the testing information is requested by the breeder and as such any information is for their records.
Posted: Tue Jul 27, 2010 4:55 pm
by Broomcroft
If the result was held on the database, it would need to cascade down through the generations as the offspring would be free by inheritance. I think that's what they do in Australia?
Posted: Tue Jul 27, 2010 5:28 pm
by dizzydex
yes I thought that would be the case for the Sire but I have been informed that the Dam can carry this gene and pass it on, is this correct then?
Posted: Tue Jul 27, 2010 6:27 pm
by Broomcroft
Yes Julie, both parents have to free of it and if they are then it's gone forever down the line, unless you re-introduce another carrier.
Edited By Broomcroft on 1280251783
Posted: Tue Jul 27, 2010 6:50 pm
by dizzydex
Right so you test your whole herd, but to keep it BDI-N you would need to keep using different bulls to grow your herd. Can a cow then be returned to her great great grand sire to produce another line or is not the done thing
Edited By dizzydex on 1280253125
Posted: Tue Jul 27, 2010 7:14 pm
by Broomcroft
It depends what you are trying to do. If you want paper proof that your herd is free of the gene, then you would need to test every breeding animal but only starting at the top. So if you tested your bull(s) and the cows you originally bought in, then get the results. If all those results were clear of chondrodysplasia, then all the offspring on your farm from those parents cannot carry the gene and cannot pass it on, so no need to test them, assuming they are Parent Verified I would have thought, otherwise I'd guess you'd need to test the lot?
Perhaps Margaret or Denise could butt in here because they know how they have done it in Australia.
Pretty hard to do all that without society involvement and a proper database I would have thought. Or at least not so meaningful.
If you just want to be free of the gene but don't want to go to the trouble and expense of testing etc, then you could simply not use any cow or bull that may be a carrier. That is what I have done and although technically I cannot say I am certified free of chondro, I also don't get any shortie calves, so it's fairly certain. After a few years it becomes statistically remote (still possible but remote) that the gene is still in the herd.
Genetically, I think it's true to say that chondrodysplasia has to show itself, it cannot hide, but in practice you can apparently get carriers that look like they may not be carriers, although I have never seen one myself.
As far as breeding a cow back to her great, great grandsire, I personally wouldn't give it a second thought because the amount of genes they would share, assuming no other relationship, is tiny, haven't got a figure but probably about 1%. But if that bull was used time and again down that line (which I assume you don't mean) then the amount of genes "shared" would be enormous (50%???) and you would be delving into the realms of extreme line-breeding. I hope I got that right'ish.
Edited By Broomcroft on 1280254789
Posted: Tue Jul 27, 2010 7:35 pm
by dizzydex
Thank you so much for taking the time to pass on all of this information. Ultimately I would like to have a Chonrodysplasia free herd.
In respect of retrurning a cow to its great great grand sire, I would only propose to do this the once.
I too would be interested to know how Australia tackled Chonrodysplasia
Thank you 
Posted: Wed Jul 28, 2010 9:53 am
by Louisa Gidney
Dizzydex, my senior bull is the product of a son on mother mating from half siblings. I haven't worked out his inbreeding co-efficient but he must be almost homozygous! I can't think that you will have any problem with putting your cow back to GGG sire. So far no signs of inbreeding depression or reduced fertility with my boy. One herd who hired him last year have now had a calf from an old cow that had not calved for 2 years, last chance for her so everyone well pleased.
Posted: Wed Jul 28, 2010 1:47 pm
by dizzydex
Hi Louisa I chose GGG Sire as I know with my Gloucester Old Spots it would possibly be ok that far back in the generations. I will let you know how I get on, I am only in the planning stages but do indend to contact the Australian Dexter Society? to get some feedback and will update with info here. Many thanks
Posted: Wed Jul 28, 2010 3:00 pm
by wagra dexters
Hi Clive and all, most people who have difficulties with the concept of maintaining a free-by-inheritance herd, chondro or PHA, don't immediately grasp that only the matriarchs of the herd need be tested, and only tested or free by inheritance (fbi) bulls are then used. Even now, some people insist that there must be throw-backs. They just don't get that gone is gone!
Initial testing wasn't such an insurmountable problem for DCAI members here because we have some wonderfully dedicated people who bent over backwards to do as much as they could to facilitate the programs, for both Chondro and now PHA. We had already been using DNA for parent verification, and blood typing before that, so genetic material was in archives for the deceased stock.
Those of us who had begun from just a couple of long-leg cows needed only to begin with having the matriarchs tested, and the society had all the bulls on the AI list tested. For those who like to breed carriers, they also benefit when wanting to avoid carrier to carrier matings, or keeping/selling carrier bulls. It is quite expensive for those who bought a larger herd initially. We have members who have spent big dollars on testing all their relevant purchases, because they wanted that science behind them, as a basis on which to make breeding decisions
There's a new dun heifer way out in the paddock tonight, no bigger than a rabbit. Conspicuous by her absence from the feeders, Mum caught my attention on dusk, but she didn't make it to the maternity ward. 3 weeks early.
Margaret
Posted: Wed Jul 28, 2010 3:42 pm
by dizzydex
Thank you so much for your reply, this has helped to clarrify a few things. Although I have a micro herd and I am trying to add to the little knowledge I have, I want to start from a point that will add value to my herd and bring long lasting results. I am certain that I will have lots more questions along the way.
Posted: Thu Jul 29, 2010 12:08 am
by Denise
Hi Julie, as an example of what we do in Australia.
this is one of our AI accredited bulls, bred and domiciled in the Uk.
quote from the DCAI herdbook
BRAMBLEDEL REDBERRY PRINCE ® (IMP UK) (ACC AI)
Identifier: DCS 4033
Sex: Male
Tattoo: UKLF0042
Birth Date: 24/05/1999
Calving Year: 1999
Status: Inactive
Registration Status: Registered
Breeder: UK BREEDER
Current Owner: UK BREEDER
Colour: Red
Horn: Horned
Grade: Purebred
DNA Case No: 21889
Chondrodysplasia: BD1: Tested Free
PHA: Tested Free
Progeny: [15 - View] [View by Herd]
BULL ACCREDITATION DETAILS: 11 August 2003
Reproductive Soundness: No defect or injury present.
Scrotal Circumference: 39 cm.
Overshot/Undershot Jaw: Neither.
Back Legs: 140 degrees.
Turned Out Front Legs: Position 2.
Cow Hocked Back Legs: Position 2.
Feet: Position 4.
Height at Hip: 116.8cm (Date of Measurement 7 July 2003).
Main Semen Distributor: Progenetics, Kurmond NSW, Ph: 041 864 041 864 4680
Fax: 02 4573 1021
Chondrodysplasia: Non carrier
As Margaret said, you need to test your base animals - i.e. your oldest cow that is the mother of your herd.
Regards