How to keep Dexters within the Breed guidelines for height

[midhilldexters]

You missed out Lasair who is listed at 41".

Carol K

[midhilldexters]

Ah ok. I saw you said breed guidelines for height twice and missed the age part.

[lakeportfarms]

Most bulls will actually grow in height until around 5-6 years old. For example, Mike was 39" at 9 years of age, certainly taller than he was at 3 years. One of his sons, LPFM MT Dylan, who we are using as a replacement for Mike, was measured 33" a few weeks ago at age 2-1/2 years. He is a chondro carrier, but he may come in below the breed guidelines at 3 years. His non-carrier progeny will likely be at the lower end of the guidelines.

[carragheendexters]

Genebo,
So what happens if you add 5 or 6inches to the height of the chondro bulls to calculate their real height if they weren't a chondro carrier?
Wouldn't a 40inch chondro carrier bull effectively be equivalent to 46 inches?

So to select for progeny to keep in the guidelines, the chondro carrier bulls would need to be 38 or 39inches tall as a max, don't you think?

[kansasdexters]

Louise,

It's just not that simple. There is enough genetic height variation in the Dexter breed that both Chondro-carrier and non-carriers can produce a rather wide range in mature height and size in their offspring. I have an example in my own herd, with Lochinvar as the sire (he was 50-inch hip height at maturity, Chondro non-carrier), bred to chondro non-carrier 44-inch hip height cow, and producing a healthy chondro non-carrier female that matured at 42-inch hip height - Wakarusa LOCH Nessa.

Ace of Clove Brook is an 11-year old Dexter bull, chondro non-carrier, and his hip height currently measures 48-inches, and his heart girth is 80-inches. But he sires small offspring (birth weights ranging from 35 to 45 lb) and, so far, they are maturing at heights that are several inches less than what their dams heights were at the same age.

If Chondro non-carriers have significant variation in the mature heights of their offspring, then chondro-carriers have even more variation, due to the effect of the chondrodysplasia allele.

What this tells me is that, like most phenotypic traits, Dexter height is a phenotypic trait that exhibits incomplete dominance, codominance, and contributions from several genes. Mature height and size are also affected by the environment and nutrition that the calf receives during the growth phases of its life.

In order to breed Dexter cattle with a uniform and predictable mature height and size, it takes several generations of careful selection without the presence of the chondrodysplasia allele. In my experience, this isn't something that can be accomplished in only one generation of breeding.


Patti

[cddexter]

Paatti, as usual your stats are impeccible. However, I think you've missed Louise's point: We all agree there is a vast variance in inherited heights among both types, but the dwarf stats are misleading. For instance, Brenn was 41.5 at 3, but because of the dwarf gene, his bones are reduced in length. This is an indisputable fact. The degree to which the chondro gene affects growth can vary slightly but on the whole it is 4-8 inches in bulls. While there may not be enough calves for us to predict an average size for his offspring especially given that the cow will have influence, too, Brenn himself, were he not a dwarf, would be more in the 46"+ range, or outside the height standard. This has nothig to do with inherited height, and everything to do with bones whose length was compromised by the chondro gene.
cheers, c.

[carragheendexters]

Hi Patti and Carol,
that was the intention of what I was trying to say, generalising using Genebo's logic.

Genebo, I was generalising about all chondro bulls not Brenn. Using your logic to select a bull for breeding for height, you would not want to use a chondro bull taller than 38 to 39 inches. The chondro bull's height is artificially shortened by the chondro gene, so the bull's apparent height would need to be adjusted up by at least 5 or 6 inches.

So using your logic to select for a bull to breed within the height guidelines, you would need to use non-chondro bulls less than 44 inches and chondro bulls less than 38-39 inches (max).

I agree Patti that selecting for height is not so simple, when breeding you are not breeding with a particular animal but with it's parents, grand-parents etc, and a myriad of factors influence final heights of animals. It is what is behind an animal that is important when selecting an animal for breeding.

Selection for height cannot be done in one generation, look how long the Trangie experiment here in Australia went for, when they were selecting for Hilines and Lowlines? At the end of the breeding experiment there was only a very small variation between the average heights of the 2 variants, don't quote me but from memory it was only something like 4-6 inches. BTW  the point of that experiment was not specifically trying to breed for 2 different heights, they were trying to identify a growth gene (this information is from a friend who is a vet who was involved in the work)

[Olga]

This is a very interesting discussion. I like the points brought up by Patti, about the variance within height of offspring with common ancestors. Those of us who have been around chondro-positive Dexters have seen how some offspring are more proportional while others are ultra-short. Well, I have seen it in our non-chondro calves as well. Some of them are born looking clearly non-chondro, while others make you scratch your head. I currently have a 9 mo old bull calf who is as tall as his 18 mo old half sister. And a 5 mo old heifer who is the same height as her 10 mo old aunt. I guess this is why in big breeds they have stats on the bulls that show what offspring one can expect and the percent of reliability of the bull's influence.

[kansasdexters]

Olga,

We see the same thing in our herd. Wakarusa LOCH Nessa has a full sister, Wakarusa LOCH Nora, and Nora has matured with a hip height of 45-inches. Same sire, same dam, same environment and diet, and both of these females are non-carriers of Chondrodysplasia, and there is a 3-inch difference in their hip height and about a 150 lb difference in their weight. Nessa's offspring are shorter and smaller than Nora's offspring, even when they are sired by the same bull. So LOCH Nessa got the short gene combination and LOCH Nora got the tall gene combination, both from the same parents.

I'm starting to believe that Dexter bulls that are not chondro-carriers may continue to grow until they are 9 or 10 years old. Since most Dexter bulls are not kept for that length of time, most people don't know what the bull's actual "mature" size really is. Ace of Clove Brook was 8-years old when he arrived at our place and he has gained 1-inch in hip height and 200 pounds in weight, over the past 2.5 years that he has been with us. He hasn't stopped growing! It will be interesting to see how long this continues and if he starts to shrink once he finally reaches "old age".

Here is a current photo of Ace of Clove Brook, 11-year old Dexter bull:




Patti

[carragheendexters]

Genebo,
I don't think that it is Carol's idea that chondro makes a difference to an animals height. I think that there is a bit or lot of science to it.
Since I first had Dexters,( maybe not as long as others on here but from before there was a DNA test,) I have owned and bred both chondro and non carriers.
It is evident in my own herd the effect that the chondro gene has on height and shape of the animal.

So what you are basically saying, if we were relating it to people, is that a dwarf person would be the same height even if they didn't have dwarfism?

[wagradexters]

Jun 23, 2014 17:59:28 GMT -5 kansasdexters said:

Patti, Bindalee Celtic Chieftain (Trillium Cluny x Woodmagic Mourning Dove 2nd) was 105cm across the hips at 2 years of age.
He continued to make height until he was 112cm hip height at 7 years old.
He did not gain any more height after that, last measured aged 11 yo.
Margaret  

[wagradexters]

Gremlins at work, the quote which is not saving is by Patti stating:
I'm starting to believe that Dexter bulls that are not chondro-carriers may continue to grow until they are 9 or 10 years old.

Margaret

[cddexter]

"It went up to 6 inches, then seven inches. In this thread right now is the first time I've read where she used the 8 inch figure."

Gene: There have been several studies done. Are you refering to Julie's study? In a copy I have she refers to 6" for cows and 8" for bulls. Can't remember if it was Gary or Jeff who quoted her at 4" and 6", as well. Since Patti is involved in this discussion and she ONLY uses stats she can prove, and my stats are frequently based on 30 years of experience seeing literally thousands of Dexters live in eight countries and via pics in four more, I tend ot err on the side of caution. If you are refering to a different study, then please share the info with us.

Thanks for acknowledging that dwarfs are genetically smaller than nons, because of the chondro gene. At no time has anyone I've seen post here ever made the claim that "all the long legged calves of short legged Dexters will be oversized".

30 years ago, it was common to see 45-47 inch non-carrier cows; and 50" bulls were out there, too. These were all 'old lines'. Gentian de la Baud was a carrier, and she was 45" tall; think how big she would have been without chondro! Briar Hill cows were running 44-47"and Jim was a major breeder and big influence on the breed for years and years. I had one of his bulls that was 47" at two. Until 20 years ago, the primary selection criteria was height, and breeders used chondro to achieve it.

Dexters aren't getting bigger, breeders are just more aware, and are selecting for different traits than they used to. It's going to take years to breed the taller genes out of the gene pool, if that's what you want. As long as the genes are there, they will manifest themselves. As long as a chondro breeder fails to acknowledge that his cute 40 inch cow is actually a 44 inch cow in a genetic girdle, and has the potential to throw large offspring, nothing will change.

This isn't about one family line, it's a generic issue within the breed. Given the history of size, for you to be ranting about a modern phenomenon of oversized Dexters is just silly.

cheers, c.

[wvdexters]

Bulls have a huge impact on their offspring and the herd. It is common practice (and a GOOD practice IMHO) to seek out the very best qualities and traits in the bull and bring them into your herd or perhaps reinforce them within your herd through him.

Improve or Maintain good udders - Choose Bull with excellent dairy qualities/ excellent udders

Improve or Maintain good feet - Choose Bull with excellent feet

etc...

Increase animal size - Choose Large Bull

[midhilldexters]

Gene,
I am someone that advertises a Chondro free herd, your accusation that I, and others that do is because we are greedy is off the wall. Why is that any different than you advertising some of your animals as being homozygous for A2? Is that you trying to be greedy?
I do it so people know I don't breed anything carrying a lethal gene.

Carol K