Starting out - Diverse views!!!

[Broomcroft]

Question 1: Does chondrodysplasia have anything good about it?

Question 2: If, as in my herd, you breed a non-carrier bull to a carrier cow, does the calf carry the dwarf gene. Yes, No, or possibly?

Some of my bigger cows seem to be more like 42-43", but they are 7+ years old. The younger ones (24-30 months) are shorter but still growing presumably. (Measured in the field very roughly).

As Kirk points out, some of my biggest steers and females have come out of a very short chondro cow. So she is actually a big cow deformed by the gene it seems.

[Saffy]

Since there are so many necks on the line already I thought I would be in good company if I added mine!

What is the difference between in breeding and line breeding?
Perhaps one of this sites genetic boffins can de mystify it for me.

To someone like me who doesn't understand the difference what I hear seems to be:

If you breed close related stock yourself you are line breeding. It is a tool to breed in specific traits, which is all good.

If your neighbour breeds close related stock he is inbreeding. It is going to magnify problems etc.

I understand the theory that if you line breed you must be willing to cull aggressively for beef anything you aren't happy with but I still don't know the difference between it and in breeding.

I don't imagine it is something that will matter to me for a long time if ever but it is a subject a few breeders have brought up and it has made me curious.

Stephanie

[Kirk- Cascade Herd US]

What is the difference between in breeding and line breeding?
Perhaps one of this sites genetic boffins can de mystify it for me.


Stephanie

There are only two types of breeding; inbreeding and outbreeding (also known as outcrossing). Inbreeding is when the the breeding pair are more closely related than the average two animals in the breed. Outbreeding is when the two animals are less closely related than the average two animals in the breed.

Linebreeding is usually defined as a type of inbreeding where a specific "line" is maintained by doubling up on a certain ancestor in a pedigree in order to maintain his/her "line". Linebreeding is often misused to describe all forms of planned inbreeding because of the moral discomfort that we humans have with even the suggestion of inbreeding in our own species.

Inbreeding in livestock can be a powerful tool used to increase homozygosity (doubling up) of good genes. Inbreeding helps to promote consistency in a herd due to having many pairs of doubled up genes. The problem is that it can also double up on bad genes. Most bad genes are recessive and can be trouble in homozygous pairs. In humans, this doubling up of bad genes is a disaster because we don't like culling our own problem offspring (even reading this sentence makes most folks uncomfortable). In livestock any doubling up of bad genes can be easily dealt with via culling.

Outbreeding (outcrossing) in livestock can be a powerful tool in the first generation to promote hybrid vigor via heterozygosity (many unlike pairings). The problem with outbreeding is that it leads to an inconsistent herd. It also allows one to hide many recessive problem genes.

Inbreeding doesn't create problems, it allows existing genetic problems to be seen. A wise breeder can use inbreeding to scrub their line of bad genes, however, you can also paint yourself into a corner if not careful, by causing some unfavorable traits to become homozygous, and then you must turn to outbreeding/outcrossing to bring in some corrective genes.

If you don't understand the power of planned inbreeding and you are not good at identifying problems and culling them, you should stay away from inbreeding yourself. However, even if you don't inbreed, you should be thrilled to acquire an excellent animal from a professional's inbred lines. These professionally inbred animals are considered prepotent and will stamp their excellence on their offspring. The professional's inbred lines are also likely scrubbed of most genetic problems. Once a line is scrubbed of genetic problems, inbreeding within that line can go on indefinitely without issues. That's why some closed herds can do so well for so long.

Hope this helps.

Kirk

[Martin]

Saffy,
buy what pleases you and what you enjoy looking at, my one pearl of wisdom on the subject. You will learn as you go on and you will change your mind about type etc. once you have your cows. You will find a favourite cow and want to keep every heifer that comes out of her in the hope that they will be exactly the same. When building a herd you will be faced with the same dilema's as the rest of us when deciding what to do with heifers at 15 months, to breed or not to breed. Choices are always to be made, which is part of the fun, I wish you well in your search for your perfect foundation animals.
I am sure you will have some great times as well as the usual occasional disapointments in your Dexter life, just enjoy them for what they are.

Martin. Medway Valley Dexters.

[Carol K]

I agree with Jo, Carrier or Non Carrier is the terminology that should be used, it's clear and concise.

I also agree with Duncan, I'm another one that doesn't like the "medium" terminology, just adds more confusion for people.

Carol

[wagra dexters]

Clive, to the second question, theoretically, half will be carriers, and half won't. If they don't have a chondro gene, they can't pass it on.

The only real proof of carrier & non-carrier is by testing. Several people have been surprised by the status of various animals, in both camps. Height is no indicator.

Our first bull, non-carrier, was 105cms at the hip at 3 years, 115cms at 5 years, 117cms at 7 years, and still 117cms at 9 and 11 years. We would not want to keep entire any that would mature over 112 now.

[Kirk- Cascade Herd US]

I agree with Jo, Carrier or Non Carrier is the terminology that should be used, it's clear and concise.

I also agree with Duncan, I'm another one that doesn't like the "medium" terminology, just adds more confusion for people.

Carol

Carrier and non-carrier is well understood by many folks, but just a note to explain that those terms are technically incorrect... The term "carry" in genetics usually means the individual "carries" a hidden recessive gene that is dominated by a dominant gene. So, for example, a black cow can carry red, but you probably wouldn't say that this black animal "carries" black - because it actually is black. Chondrodysplasia is a dominant gene (actually a type of dominance called co-dominance). Technically speaking, if an animal has a chondrodysplasia gene, it is affected and must exhibit it. Therefore, technically, it doesn't "carry" the gene. "Chondrodysplasia affected" is the most accurate term (but a little more clunky than "carrier". I usually use chondrodysplasic vs. non-chondrodysplasic as more technically correct terms, but I understand the common use of "carrier".

Also, most other breeds have scrubbed their herds of various dwarfism genes, yet they still have smaller, moderate, and larger lines within their breeds. I believe those other breeds use terms such as large framed, small framed, and perhaps "moderate" framed to describe the different sizes of animals within their breeds?

If I am to clearly communicate the stature and chondrodysplasia status of my herd, would "moderate framed, non-chondrodysplasia" communicate that clearly to you? Would "small framed, non-chondrodysplasia" clearly communicate the type of the Woodmagic herd? Would "large framed, non-chondrodysplasia" accurately describe a 49 inch bull? If not, what terms would you use?

Kirk

PS. I really love our moderate framed, non-chondro Dexters and probably would continue to do so even if they were a little shorter or a little taller.

[Broomcroft]

The only real proof of carrier & non-carrier is by testing. Several people have been surprised by the status of various animals, in both camps. Height is no indicator.

Well here we go again, "Height is no indicator". Gems of knowledge. I was certain, even after reading this board as best I can, and I do literally need new glasses, that not all Short dexters were chondro, that is very clear, but I was also totally convinced that all Longs were clear of the gene. i.e. that chondro was restricted to Shorts.

I am fairly sure that most people who do not have a good background in Dexters, think that all or most Shorts have the gene, and that Longs/Non-Short do not.

Is there anywhere, where all this knowledge has been gathered together and published so it can just be referred to as the Dexter bible? Why don't you all write a book, send me the text and I'll put it on a special web site. www.thedexterguide.com, or www.dextersfordummies.com. :D

Or are we saying that there are tall Shorts...in which case my brain has just seized up again!

[Kirk- Cascade Herd US]

that not all Short dexters were chondro, that is very clear, but I was also totally convinced that all Longs were clear of the gene. i.e. that chondro was restricted to Shorts.
are we saying that there are tall Shorts...in which case my brain has just seized up again!

Imagine a class of school kids. Let's assume that none of these have the very rare human dwarfism gene that is similar to Dexter chondrodysplasia. There are tall kids, short kids, thick kids, skinny kids, etc., all without dwarfism, just due to the myriad of genetics that affect size and height. Picture that the tall kid probably came from some tallish parentage and the short kid probably came from some shortish parentage.

Now imagine another classroom filled with the same assortment of kids, but one also has a dwarfism gene. If it's the kid from the tall family, he will almost certainly be the shortest one in his tall family, because the gene definitely impacted him, but he might still be a little taller than the shortest kid in the class. So if you had to guess which kid had the gene, you couldn't just pick the shortest kid. But, you could probably safely assume that the tallest half of the kids in the class don't have the gene and would almost always be correct.

Chondrodysplasia interferes with normal frame growth that is controlled by many other genes. Cows with otherwise tall genetics are made shorter by chondrodysplasia interfering with normal growth. Cows with otherwise short genetics are made even shorter due to the dwarfism gene. A 41 inch chondrodysplasic bull from a line of 50 inch bulls, might still be taller than the shortest non-chondro bulls.

99 percent of the time, those animals that clearly are the tallest and longest legged in your herd of mostly non-carriers are free from the gene, but why not test to make certain? Does anyone disagree?

[Broomcroft]

I understand at last. I often take a long time getting there! Thanks to all for putting me straight.

[Sylvia]

Clive, I'll join you in a home for the bewildered. Will your wife do the cooking? If so, I'm packing now.

I don't think the shoulder or topline height matters one bit in carrier terms, I think it is the leg length at birth which matters. Short-legged Dexters (and I bet these are what everyone not connected with the breed think of as 'proper' Dexters) are all carriers. Non short (or normal) length legs at birth spell non-carriers. I stress at birth because long legs can look shorter as animals mature and sort of grow down as the body deepens.

Well that's my tuppence worth. Sorry, Kirk, I know you are trying to make things as simple as possible for us dimbos but what with the continuous rain here and no harvest in yet I think what was left of my brain has rusted up.

[Saffy]

Thank you Kirk, ( a few posts back now,) for the line breeding/in breeding explanation. I really think I understood!!! :D

Also Martin your suggestion I buy what pleases me is of course what I will do eventually but the more I can learn before I decide what pleases me the less likely I am to change my mind.

At the moment I am still leaning heavily toward the smallest but chunkiest type, best conformation, non short I can find within my price range.

As I don't envisage selling much, if any beef, (though we intend to eat it ourselves,) I don't feel I need to worry about the opinion of the butcher.

It doesn't seem right to me to try to breed bigger dexters as surely the whole point is that they are small cows.After all big cows are being done quite well by countless breeds.......its OK my head was still on the block from before!

Stephanie ???

[Rob R]

I agree with Jo, Carrier or Non Carrier is the terminology that should be used, it's clear and concise.

I also agree with Duncan, I'm another one that doesn't like the "medium" terminology, just adds more confusion for people.

Carol

Ditto

[Duncan MacIntyre]

Perhaps I phrased what I meant badly. What I would like to do is to produce a strain of non- chondrodysplastic dexters which are the same height as the ideal chondrodysplastic specimens. I am confident that it can be done. If I do it myself and no one else joins in, it will of course amount to nothing. But if we can create a substantial number of these, enough to allow selection of the best, then we will have all the good points and genetics of the Dexter in a true breeding animal of the size that everyone traditionally expects the Dexter to be. There will then be no need to rely on chondrodysplasia to produce show size Dexters.

I find it impossible to believe that the ancient Irish relied on a breed producing 25% bulldogs, or messed about with longs and shorts etc. They would have had a good true breeding small breed, or more likely regional variety, of cattle. I have suspicions but no proof that the chondrodysplasia gene multiplied when it gave an easy way to produce a visually beefier type, and was eagerly grabbed by the rich and famous who brought the breed to England in the mid 1800's, almost certainly without realising what they were doing. But buried deep in the breed are the genes of the sustainable true breeding smallholder/poor man's cow. That can be brought out again by inbreeding the right sorts.

Duncan, neck really on the block this time.

[Saffy]

Sounds spot on to me Duncan.

Small cow that always produces similarly small calf with no threat of a bulldog. Ideal?!

Its OK I'm new .....nobody knows where I live!!!

Stephanie