EDUCATIONAL INCUBATION & HATCHING CHAT THREAD, w/ Sally Sunshine Shipped Eggs

[DwayneNLiz]

What gene is that?

I have a nephew that raises them.

short leg dwarfism

http://www.dextercattle.org/adca/adca_article_chondrodysplasia.html

With the advent of the science of genetics, it was discovered that the very trait that made a Dexter a Dexter (short legs), was unfortunately due to a form of dominant lethal genetic mutation. As long as the mutation was the primary selection criterion, all three types would continue, and Dexters would never breed true. Rather than give up the appearance they preferred, owners chose to live with the problem.
Once the mutation was better understood, many started to breed their shortleg Dexters with the normal as they found they still got the same proportion of shortlegs but avoided the bulldog calves. For those matings, the statistical proportions were ½ shortleg, ½ normal. Until very recently, owners continued to breed both ways, with only the shortleg considered the real Dexter, and many (most) of the longlegs discarded. Since 1980 in North America, some owners have chosen to breed small longlegs, working to produce a size and look similar to the original selection criteria, but without using the lethal mutation.

 

[ChickenCanoe]

I just found this from dextercattle.org.

With the advent of the science of genetics, it was discovered that the very trait that made a Dexter a Dexter (short legs), was unfortunately due to a form of dominant lethal genetic mutation. As long as the mutation was the primary selection criterion, all three types would continue, and Dexters would never breed true. Rather than give up the appearance they preferred, owners chose to live with the problem.
Once the mutation was better understood, many started to breed their shortleg Dexters with the normal as they found they still got the same proportion of shortlegs but avoided the bulldog calves. For those matings, the statistical proportions were ½ shortleg, ½ normal. Until very recently, owners continued to breed both ways, with only the shortleg considered the real Dexter, and many (most) of the longlegs discarded. Since 1980 in North America, some owners have chosen to breed small longlegs, working to produce a size and look similar to the original selection criteria, but without using the lethal mutation.

The Mutation:
Dexter cattle have a unique genetic mutation that causes defective bone growth. This mutation is referred to as chondrodysplasia, and it results in the animals appearing heavy bodied on short legs. There is a large variation in effect of this single-gene mutation, with some animals being proportionate and very attractive, while others are strongly disproportionate with a dwarf-like appearance. The degree of dwarfism expressed is not consistent. At this time, the cause for the variation is not known. Carriers of this gene appear to be much more heavily muscled, but this is because muscle that is designed to attach to a normal bone is actually compressed onto a shortened one, causing the muscle to bulge. Carriers often show a greater spring of rib or can be potbellied because the organs retain their normal size yet must fit within the reduced skeletal framework, or drop below it.

 

[DwayneNLiz]

we strike again

 

[DwayneNLiz]

12: Carrier
In the case where both genes are affected, all chondrocytes are disorganized. No palisading takes place, and there is virtually no bone growth. The fetus is aborted most frequently either between 30 and 60 days (information provided by experienced English breeders with large herds; less experienced owners think the cow simply didn’t settle and rebreed her) or between 6 and 8 months (in which case the fetus has vestigial legs, an abdominal hernia and a ‘bulldoglike’ head). This is the Dexter ‘bulldog’, always born dead, hence the genetic designation ‘lethal.’

 

[daxigait]

What gene is that?

I have a nephew that raises them.

I just remember seeing it in my research. I am not able to look it up right now.

 

[ChickenCanoe]

we strike again

That's absolutely hilarious.

I just remember seeing it in my research. I am not able to look it up tight now.

That's OK, I found it.

I've seen dwarfism in Angus.

 

[ChickenCanoe]

...

So what you're telling me is that if I want to start a /beef/milk/draft project in Costa Rica, I should rethink paying to transport Dexters internationally?

 

[DwayneNLiz]

So what you're telling me is that if I want to start a /beef/milk/draft project in Costa Rica, I should rethink paying to transport Dexters internationally?

not necessarily, just use good starting stock, with long legs




The combinations below are statistical probabilities. Every calf is a new throw of the dice. There is no specific bias toward any one direction; no inclination to one result over another. It is all pure chance. The possible statistical genetic combinations are:
Non-carrier bull x non-carrier cow:

100% chance of having a non-carrier calf
Non-carrier bull x carrier cow:

50% chance of having a non-carrier calf


50% chance of having a carrier calf.
Carrier bull x non-carrier cow:

50% chance of having a non-carrier calf;


50% chance of having a carrier calf.
Carrier bull x carrier cow:

25% chance of having a non-carrier calf;


50% chance of having a carrier calf;


25% chance of having a dead bulldog calf.
A quick examination of the above breeding statistics makes it clear that only the non-carriers breed true. For those who wish to breed the carrier, both types will be produced, creating a herd that shows a wide range of heights because of the effect of the mutation.
Because we are dealing with a form of dominant gene, many carriers can be identified visually. However this does not hold true 100% of the time. Only genetic testing can identify the presence of the mutation. With that knowledge, owners can make informed breeding choices.
The ADCA recommends that owners who wish to breed the carrier type mate carriers with non-carriers to avoid their cows having bulldog calves.
For the instructions and application for Chondrodysplasia testing please click here: - Chondrodysplasia Test Form

Those who test will receive test result certificates from Texas A&M, the official ADCA DNA lab.
Here is the test result interpretation table that appears on the reports:

 

[kwhites634]

Quote: It was dead on here last night, so I went down about 9:30. Got 8 hours in, as opposed to my usual 7.

 

[DwayneNLiz]

So what you're telling me is that if I want to start a /beef/milk/draft project in Costa Rica, I should rethink paying to transport Dexters internationally?

and the testing is relatively inexpensive, only $20 for the lethal gene test