Bulletin Readers Letter

[Woodmagic]

Unless it is a small animal clear of the recessive – non-carrier, any short leg will have one bulldog gene that has reduced their own skeleton size. The second gene will be normal, and the calf has to collect one of those two. The calf can only collect two bulldog genes if both parents possess one and both pass on the dud one. Providing you use a long leg for one parent the calf can only collect one or none. It is exactly the same as tossing a coin that can come down heads or tails. A short leg bull will eject 1,000’s of sperm, half of which will carry the recessive, and it is a case of who wins the race. Providing one parent is short, calves from the same mating can come out short or long, looking utterly different. Both parents, bull and cow, possess two genes for everything, including the blue print for skeleton development, which of the pair they pass onto the calf is pure chance every time.

[Colin]

So unless I'm mistaken (please confirm Beryl), neither the normal nor BD gene is dominant or recessive. In other words neither gene completely masks the other. So you need two normal genes for a non-short, two BD genes for a BD calf, and a mixture of a BD and a normal gene results in a short leg.

Colin

[GRAEME]

read the letter three times and although its not too upsetting I do feel its a little misguided. Whats wrong with a niche market? I think most dexter beef producers would be only too happy with that tag. The author seems to think that competition is about volume, in this case its not its about quality not quantity, thats what we compete on. The niche also is about a lot more than just fillet, everything I have produced from a dexter is superior to what I buy in the supermarkets.
I do believe the author has a point about increasing size and thought has to go into how that can be controlled in future. I would also take exception to the comment that putting non short to non short will increase size surely that is not correct and in some ways its desireable if the non shorts are good true specimens?

[Woodmagic]

For the last thirty years I have bred non-short to non-short, and in the process have reduced to a much more level herd with the size of the biggest down by around 5”. The size range was originally from 36”-46” it is now 40”-41”

[AlisonKirk]

Graeme - My comment re breeding non-short on non-short....I was corrected on this point by my husband. I can confirm we do use non-short on non-short sometimes and yes, we do have a nice level herd.

I was merely trying to figure out how breeders would get their Dexters bigger without introducing another breed.


Alison Kirk
Boram Dexters

[Woodmagic]

Colin, you are correct, if the bulldog gene were a true recessive you would not have short leg Dexters in the traditional sense. It can usually be seen in the carrier, although the extent to which it shows varies. I find it is demonstrated to a greater extent once the animal has reached three years, up to that point the skeleton is usually growing, but unlike the non-carrier the skeleton growth slows down in the carrier at three, while the non short will tend to continue for another two years in tandem with the carcass.

[Kirk- Cascade Herd US]

So unless I'm mistaken (please confirm Beryl), neither the normal nor BD gene is dominant or recessive. In other words neither gene completely masks the other. So you need two normal genes for a non-short, two BD genes for a BD calf, and a mixture of a BD and a normal gene results in a short leg.

Colin

The chondrodysplasia gene (lethal) actually is a type of dominant gene called a co-dominant. This means that it cannot hide, but must exhibit every time. It also means that the normal gene is also co-dominant and must exhibit every time. So when a dexter has both genes (normal and chondrodysplasia), both genes exhibit and thus you get a watered-down and survivable version of chondrodysplasia (half normal and half chondrodysplasia). However, when there are two chondrodysplasia genes, then you get the full effect of the gene and it is lethal.

Kirk

[Kirk- Cascade Herd US]

I was merely trying to figure out how breeders would get their Dexters bigger without introducing another breed.


Alison Kirk
Boram Dexters

Ignoring chondrodysplasia (a dwarfing gene) for a moment, height in animals is polygenetic, meaning that there aren't just one or two simple genes controlling height. Instead, many genes in combination have an effect on the height of an animal. These genes may do all sorts of things like controlling growth periods (age at which growth slows), controlling digestion (making the animal more efficient in converting food - resulting in a larger animal), controlling mineral translocation (making calcium available for bone growth), etc.

Some of the myriads of combinations of these many genes will result in larger animals and some combinations will result in smaller animals (within the maximum and minimum potential for the breed). So without going outside of the breed, by simply selecting the largest animals each generation, you would unknowingly be selecting the combinations of the many genes affecting size that give you the largest possible pure Dexters. Likewise, by selecting the shortest animals (remember, we're setting aside the dwarf gene for a moment), you are unknowingly selecting for combinations of genes which give you smaller Dexters. With literally tens of thousands of possible different combinations of the polygenetic genes affecting size, there's a lot of room for resulting variation. It would appear that the Woodmagic herd has focused on the smaller possible combinations.

Now if we allow back into this mix, the chondrodysplasia (dwarfing) gene, it has no affect on the animal's regular genetics. So when you add the chondrodysplasia gene to an animal that has a combination of sizing genes that codes for maximum size, then the chondrodysplasia gene shortens the animal and masks its "true" large-size genetics. So, you can have a very genetically "large" dexter that looks short. This animal will pass its large set of genes to all of its calves, but the chondrodysplasia gene will mask those large genetics in 50% of the calves.

Kirk

Cascade Herd

PS. The word "Dwarf" in genetics is the standard word for a variety of simple genes that interfere with normal growth processes and result in a reduced size plant or animal. These plants and animals still have most all of their normal size genetics intact.

[welshdexterboy]

Thanks for that Kirk i think i understood it after the third reading. So is the non-short the true size of a Dexter?

Do you deal with genetics etc in your work Kirk or just read a lot?:)

[Colin]

Thanks Beryl and Kirk for that very informative feedback.

As a newcomer who has used this Discussion Board for 3 months, I find it a gold mine of information from people with a wide variety of practical and scientific knowledge and experience. So Mark it's a superb asset for the Dexter community. Its key strength in my view is the willingness of its community of members to actively contribute, enabling a healthy discussion and, for people like myself, access to hundreds if not thousands of years of cumulative experience. It's a shame the writer of the letter doesn't pursue gaining access as I don't believe he or she will find a rift between purists and commercialists, but a healthy and constructive discussion. And from what I've read, there seems to be pretty much consensus on the way forward in terms of the market positioning of Dexter beef versus the mainstream commerical breeds.

Colin

[happy hollidays]

It is my understanding that the Dexter is "famous the world over" for its size and its hardiness and maternal qualities, not to mention its is an economical breed to raise. We should not allow these to change, if you want bigger cattle, then you should change breeds quite simply, not change the Dexter. In order to increase profits I believe the DCS should be actively pursuing reduced slaughter costs for example and equally be active in ensuring the breed is kept small. This site is wonderful, it gives the opportunity for different types of Dexter owners to communicate, ask questions, debate, disagree and much more. I feel it is disgraceful that DCS publish such letters, somethings are better off keeping quiet until they can be shared in a more sensitive way.

[Kirk- Cascade Herd US]

Thanks for that Kirk i think i understood it after the third reading. So is the non-short the true size of a Dexter?

Do you deal with genetics etc in your work Kirk or just read a lot?:)

Many different theories exist about the source of Dexters and the historical role of the chondrodyplasia gene. Some believe the breed started without the gene and the gene was added later, and some feel it was there since the beginning and defines Dexters. At this point in time, I would say that the "true" breed consists of a rather wide range of sizes; small, smaller, smallest, some with Chondrodysplasia and many without. Our animals on our farm are somewhere between small (the larger Dexters) and smaller (medium sized dexters) and are all without the chondro gene. We like the moderate sized Dexters (not too large, and not too small). I don't personally like the chondro gene, because I want our herd to be very consistent and the gene masks the true size genetics making it hard to breed for consistency.

I believe that since Dexters are raised for personal enjoyment, that if you understand the chondrodysplasia gene and choose to use it for your own satisfaction, that's fine and dandy or if you choose to eliminate it in your herd that's fine too. But I do feel strongly that people should make a well informed choice based on a good deal of information about all of the options.

Concerning my background, I have bred various animals and plants since I was just a kid (forty years ago). I took biology and genetics courses in college (but ended up in computer software). I also took many statistics courses where genetics are used as prime examples of permutation and combinational statistics and I had a knack for that. Then, with the many breeds of animals on our farm, I do tons of research and seeing the interrelationship of genetics between goats, cows, pigs, colored sheep, livestock dogs, etc. and that really helps me understand it all. For example a dun dexter and a chocolate lab dog get their colors from the same genetic mechanisms. A red Duroc pig and a true-red cow have the same color genetics.

I'm definitely not a professional and I still have much to learn.

Kirk

[Woodmagic]

[It would appear that the Woodmagic herd has focused on the smaller possible combinations].
[Some believe the breed started without the gene and the gene was added later, and some feel it was there since the beginning and defines Dexters]
Most geneticists are agreed that the breed would not have survived for centuries in the wild with the recessive. Certainly this was my own experience. For the first eighteen years I used a short leg but did not discriminate in the cows that I kept, except on commercial grounds – i.e. providing that a cow milked and produced she was retained, regardless of type. On this regime, the long leg became preponderant, because they lived longer overall. Of one bull’s progeny after ten years, I had only three of the short out of ten, but the three long he had sired were still with me.
This was when I took stock, I looked for an animal, which within that population was surviving and looked as near to a ‘true’ Dexter as possible. Using her as dam for my bulls, she bred true. I never bred down to size; I took what nature offered. If, as I suspect, a dwarf of another breed brought in the bulldog - the most likely candidate for a cross, it would inevitably give a bigger animal when the bulldog was removed. This type of non-carrier was common at the time, around 40”, but the short was favoured in the show ring, it has a beefier appearance. The same thing occurred with many beef breeds around the ‘20’s and took several years before most breeds eliminated their dwarves.

[Saffy]

I have posted the image below as an illustration for the next woodmagic post.

Stephanie

[welshdexterboy]

Are they your cows Saffy or is one a steer? can you tell me what height they are? They look a credit to you anyway whatever they are.