I agree with Woodmagic concerning not enough emphasis placed on cows (it would be hard to disagree with such amazing experience). My emphasis on bulls was only because that's usually what people shop around for come breeding time, it's even more critical at cow selection time.
Our crop of 2006 calves certainly displays what Woodmagic is saying about cows being very important. It's shocking how each of our calves is an image of their mothers. We are trying to produce our own replacement bull, and I agree that our most important piece of information is the quality of the dam. An excellent calf from a poor Dam can be hiding all sorts of poor genetics.
Kirk
Inbreeding? - What are ther rules and risks?
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JamsHundred
- Posts: 134
- Joined: Sat Nov 19, 2005 4:14 am
This has been a very informative and interesting thread. Thanks for contributing !
I have a question for the genetics expert, or anyone who knows the answer.
How many generations can a recessive gene lie hidden? Forever? I am primarily interested in the genetics of the color red, which I am researching with a friend. There are two red animals in particular of interest in the US herd, ( both tested red), who have nothing but a sea of black cows in their pedigrees for generations and generations. Can a recessive gene be passed indefinitely without being expressed?
I have a question for the genetics expert, or anyone who knows the answer.
How many generations can a recessive gene lie hidden? Forever? I am primarily interested in the genetics of the color red, which I am researching with a friend. There are two red animals in particular of interest in the US herd, ( both tested red), who have nothing but a sea of black cows in their pedigrees for generations and generations. Can a recessive gene be passed indefinitely without being expressed?
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Kirk- Cascade Herd US
- Posts: 267
- Joined: Tue Aug 29, 2006 7:21 am
A recessive gene can lie hidden forever or show up rather quickly. It's a matter of statistical probability. Those probabilities can be shifted by inbreeding or outcrossing. Rare recessives are more likely to double up and exhibit themselves with a lot of inbreeding and are more likely to remain hidden with much outcrossing (assuming the outcrosses don't carry the recessive).
Let's say you have a closed herd of 101 animals consisting of one homozygously black bull, 99 homozygously black cows, and one heterozygously black cow carrying one red gene. Let's assume that you use your bull for two years, and then replace him with one of his sons, use the replacement for two years and then replace, etc., such that no bull is breeding his direct daughters, but you allow for inbreeding other than that. Let's also assume that you steer nearly all of the males, and you sell off many of the heifers and cows in order to maintain 101 animals.
Until your next replacement bull carries red and that bull breeds a heifer that also carries red you have no chance of producing a red calf. Given that most of the animals are homozygously black, it could easily be 100 years or more before the replacement bull you choose happens to be out of one the cows carrying red and he also happens to get the red gene from his mother, and he breeds a red-carrying cow and both he and the red carrying cow both contribute the red gene.
All that being said, one has to keep in mind that probability statistics just predict the chance of something occurring not the possibility of it occurring. It is possible (but very unlikely) that the herd in the example could have it's first red calf within the first 3 years and it's possible (but unlikely) that a red calf would never ever show up in a million years.
It's possible and probable that a red calf in this example would show up within 100 or 200 years and someone ambitious could compute that probability percentage. The example contained a degree of inbreeding, with less inbreeding, the probability of the recessive doubling up would be even less.
I hope this helps and hope even more that it makes sense.
Kirk
PS. Sorry for the long post
Let's say you have a closed herd of 101 animals consisting of one homozygously black bull, 99 homozygously black cows, and one heterozygously black cow carrying one red gene. Let's assume that you use your bull for two years, and then replace him with one of his sons, use the replacement for two years and then replace, etc., such that no bull is breeding his direct daughters, but you allow for inbreeding other than that. Let's also assume that you steer nearly all of the males, and you sell off many of the heifers and cows in order to maintain 101 animals.
Until your next replacement bull carries red and that bull breeds a heifer that also carries red you have no chance of producing a red calf. Given that most of the animals are homozygously black, it could easily be 100 years or more before the replacement bull you choose happens to be out of one the cows carrying red and he also happens to get the red gene from his mother, and he breeds a red-carrying cow and both he and the red carrying cow both contribute the red gene.
All that being said, one has to keep in mind that probability statistics just predict the chance of something occurring not the possibility of it occurring. It is possible (but very unlikely) that the herd in the example could have it's first red calf within the first 3 years and it's possible (but unlikely) that a red calf would never ever show up in a million years.
It's possible and probable that a red calf in this example would show up within 100 or 200 years and someone ambitious could compute that probability percentage. The example contained a degree of inbreeding, with less inbreeding, the probability of the recessive doubling up would be even less.
I hope this helps and hope even more that it makes sense.
Kirk
PS. Sorry for the long post
The passing on of genes is more easily explained if you think of the DNA as being like a zip. When an egg (cow) or a sperm (bull) is being made, it only gets one side of the zip. The lining of the testes and the ovum have cells that only produce one strand of RNA. When the egg and sperm fuse, the two different RNA strands zip up into a new DNA strand. This double helix then replicates itself by a photocopy method, building a new animal.
The single strand of RNA will contain a mix of both Dominant and recessive genes. Its only when its recombined (zipped up) with the new RNA from the other parent, that the DNA is able to decide which type of Allele is now in control over a specific part of the new animal.
Hopefully two recessive detrimental genes don't get matched up in the recombination, but its always a gamble as to which gene is going to be passed on to the new generation.
Now is that any clearer?
The single strand of RNA will contain a mix of both Dominant and recessive genes. Its only when its recombined (zipped up) with the new RNA from the other parent, that the DNA is able to decide which type of Allele is now in control over a specific part of the new animal.
Hopefully two recessive detrimental genes don't get matched up in the recombination, but its always a gamble as to which gene is going to be passed on to the new generation.
Now is that any clearer?
Inger
NZ
NZ
It has to be remembered that the one ‘zip’ donated to the calf, includes various pieces of the two ‘zips’ that parent inherited, no two calves will receive exactly the same combination, and looking at a grand parent often shows more of the inheritance than the parent.
How refreshing to read something by folks who obviously knows their genetics, and are using it in the realm of Dexters. The explanation of the hidden red sadly mirrors my own experience.
I started with a black herd and the odd red, and a bull that carried it, unfortunately I managed to ‘lose’ it completely, within a few years.
After I had embarked on a closed herd and had to accept that I had become totally black or dun, I sold a bull calf into the Templeton herd, the first calf he sired was red. I couldn’t even borrow him, because by then I had become IBR free!
I can confirm the extent to which the dam will influence the calf. Although I have inbred for years, using the same bull over the entire herd, my female families still maintain a distinct individuality. Whether this is due solely to mitochondrial influence, or whether there is some other reason I don’t know, genetics hasn’t all the answers yet.
My herd has numbered between thirty and sixty; it is around 40 years since I last bred a red. Now that it is possible to do a DNA test for red, I thought I might embark on an examination of one or two animals that show a suspicion of red on the withers, it can be a sign that they are carriers, and I have my eye on one in particular. I would love to bring the red back into the Woodmagics.
How refreshing to read something by folks who obviously knows their genetics, and are using it in the realm of Dexters. The explanation of the hidden red sadly mirrors my own experience.
I started with a black herd and the odd red, and a bull that carried it, unfortunately I managed to ‘lose’ it completely, within a few years.
After I had embarked on a closed herd and had to accept that I had become totally black or dun, I sold a bull calf into the Templeton herd, the first calf he sired was red. I couldn’t even borrow him, because by then I had become IBR free!
I can confirm the extent to which the dam will influence the calf. Although I have inbred for years, using the same bull over the entire herd, my female families still maintain a distinct individuality. Whether this is due solely to mitochondrial influence, or whether there is some other reason I don’t know, genetics hasn’t all the answers yet.
My herd has numbered between thirty and sixty; it is around 40 years since I last bred a red. Now that it is possible to do a DNA test for red, I thought I might embark on an examination of one or two animals that show a suspicion of red on the withers, it can be a sign that they are carriers, and I have my eye on one in particular. I would love to bring the red back into the Woodmagics.
I optimistically imagined I had long enough ahead of me!!! I would hope to breed a bull with the recessive and in time to produce a red bull. I suspect if I find she carries it, I will try one or two others I think are possibles. It would shorten the odds. The afore mentioned bull is long dead, and bulls have to be tested for IBR if semen is to be taken. I shall wait and see what the Cardiff results are first. Surely there is a bull out there with a long pedigree.
Infectious Bovine Rhinotracheitis is a respiratory disease. It is extremely common in this country, and there are very few herds at the moment that are IBR free. An eradication programme is in operation in many European countries. I went IBR free when it became necessary if I wished to continue my exports to Denmark, at which point BSE and full stop----.
I kept up my status, but believe I am almost the only Dexter herd, and when I last heard, there were only about 90 herds overall. At present there is a campaign to encourage more participation to enable exports to Europe.
I kept up my status, but believe I am almost the only Dexter herd, and when I last heard, there were only about 90 herds overall. At present there is a campaign to encourage more participation to enable exports to Europe.
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Duncan MacIntyre
- Posts: 2372
- Joined: Tue Mar 30, 2004 12:38 am
- Location: Isle of Bute, Scotland, UK
What an interesting thread this has been. I have been having a wee holiday from contributing for a variety of reasons, far too many things to do for one, and a torn calf muscle about a month ago which seemed to affect my brain power. Thankfully now healing, I have thrown away the sticks and can walk normally. All serves me right for sprinting along side 17 year olds when old enough to be their grandfather.
Anyway, this thread has had some very useful posts. Most questions about inbreeding seem to arise when someone has accidentally come against it, through an unexpected mating or lack of alternatives for some reason. I think most people seem to have an unreasonable fear of it on this one-off basis - it is most unlikely that the resultant calf is going to be some sort of dreadful monster with three heads and two tails. So if for some reason one close mating is happening do not be too afraid. Another fear which seems to take hold is of using an animal which is the result of inbreeding. If you see an animal at a sale which is inbred, and looks good, then go for it - because of the inbreeding and lack of visible faults it is likely to pass these characteristics on, and is very safe to use in an outbreeding herd.
On the other hand if a breeder is deliberately entering into an inbreeding plan then they should read up well and be prepared to accept that as the degree of homozygousity increases then more recessives will show up. If they are good genes, fine, but they are just as likely to be detrimental so a number of calves may result which have to be culled, or at least not continue to be used for breeding in that herd though they might be OK if outcrossed with different lines.
In my own herd I am using inbreeding to try to produce Dexters of traditional short leg size but not carrying the bulldog gene. In 2000 I purchased a bull calf, Shilton Pontius, who though he does not carry the Woodmagic prefix is of pure Woodmagic lines. At two and a half years old he was just 40.5 inches at rump, now just a bit over 42 inches, fairly beefy, good level top line, good feet and legs. Probably tail set a little high is his most obvious fault. The females of the herd when I began using Pontius were from a female line descended from a cow called Cuerden Cindy, polled, not too big, good general conformation. Over different generations sires used included Canwell Buster, Ilsington Bramble, Saltaire Foxhound and Saltair Diamond. Daughters of Pontius of suitable size have been mated with sons of Pontius from different dams within the herd, and the resulting granddaughters if they are suitable will be mated to Pontius. All has gone well so far except for one calf which showed a bit of white in front of navel. Within the next year or two I hope to have some heifers which meet my ideal for size, all gauranteed bulldog free. I am not too worried about colour, and have all three in the herd. I am not too worried about polled, and have a number of polled individuals, but size and type is the priority.
The females currently in the herd include a Pontius daughter and three granddaughters, and visitors in 2006 have all commented on the uniformity of them. One visitor from USA accused me of using a "Cooke Cutter".
The worst handicap has been only having one heifer calf in the last two years, and lots of bulls. Saltaire Drill, my only cow not related to Pontius, is due shortly, here's hoping for a heifer.
Lastly, Sylvia asks for a list of ALL diseases we should be trying to stay free of. How long a list would you like, Sylvia? I will start a new thread on this topic.
Duncan
Anyway, this thread has had some very useful posts. Most questions about inbreeding seem to arise when someone has accidentally come against it, through an unexpected mating or lack of alternatives for some reason. I think most people seem to have an unreasonable fear of it on this one-off basis - it is most unlikely that the resultant calf is going to be some sort of dreadful monster with three heads and two tails. So if for some reason one close mating is happening do not be too afraid. Another fear which seems to take hold is of using an animal which is the result of inbreeding. If you see an animal at a sale which is inbred, and looks good, then go for it - because of the inbreeding and lack of visible faults it is likely to pass these characteristics on, and is very safe to use in an outbreeding herd.
On the other hand if a breeder is deliberately entering into an inbreeding plan then they should read up well and be prepared to accept that as the degree of homozygousity increases then more recessives will show up. If they are good genes, fine, but they are just as likely to be detrimental so a number of calves may result which have to be culled, or at least not continue to be used for breeding in that herd though they might be OK if outcrossed with different lines.
In my own herd I am using inbreeding to try to produce Dexters of traditional short leg size but not carrying the bulldog gene. In 2000 I purchased a bull calf, Shilton Pontius, who though he does not carry the Woodmagic prefix is of pure Woodmagic lines. At two and a half years old he was just 40.5 inches at rump, now just a bit over 42 inches, fairly beefy, good level top line, good feet and legs. Probably tail set a little high is his most obvious fault. The females of the herd when I began using Pontius were from a female line descended from a cow called Cuerden Cindy, polled, not too big, good general conformation. Over different generations sires used included Canwell Buster, Ilsington Bramble, Saltaire Foxhound and Saltair Diamond. Daughters of Pontius of suitable size have been mated with sons of Pontius from different dams within the herd, and the resulting granddaughters if they are suitable will be mated to Pontius. All has gone well so far except for one calf which showed a bit of white in front of navel. Within the next year or two I hope to have some heifers which meet my ideal for size, all gauranteed bulldog free. I am not too worried about colour, and have all three in the herd. I am not too worried about polled, and have a number of polled individuals, but size and type is the priority.
The females currently in the herd include a Pontius daughter and three granddaughters, and visitors in 2006 have all commented on the uniformity of them. One visitor from USA accused me of using a "Cooke Cutter".
The worst handicap has been only having one heifer calf in the last two years, and lots of bulls. Saltaire Drill, my only cow not related to Pontius, is due shortly, here's hoping for a heifer.
Lastly, Sylvia asks for a list of ALL diseases we should be trying to stay free of. How long a list would you like, Sylvia? I will start a new thread on this topic.
Duncan
Duncan MacIntyre
Burnside Dexters 00316
Burnside
Ascog
Isle of Bute
Burnside Dexters 00316
Burnside
Ascog
Isle of Bute
Sorry to hear about your poor old leg Duncan, but at least you weren't hang gliding like an ex vet of mine who broke her leg. I was sympathetic until I heard what she was doing. Don't you vets get enough excitement at work?
As for the cattle diseases, possibly the ones which might be lurking in an apparently healthy herd might be useful. I find it alarming that my herd probably has IBR because it hasn't been proved IBR free. Sounds like guilty until proved innocent to me and we all know that ignorance of the law is no excuse. Maybe someone else would have a better idea.
As for the cattle diseases, possibly the ones which might be lurking in an apparently healthy herd might be useful. I find it alarming that my herd probably has IBR because it hasn't been proved IBR free. Sounds like guilty until proved innocent to me and we all know that ignorance of the law is no excuse. Maybe someone else would have a better idea.
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JamsHundred
- Posts: 134
- Joined: Sat Nov 19, 2005 4:14 am
I am not a scientist nor a genetics guru, but I am a keen observer, and I am not comfortable with the "assumption" that recessive genes in general, and the color red in particular are carried hidden for generation after generation after generation without expressing themselves. Three herds that have been closed for decades have not bred reds of which I am familiar. Woodmagic has dun in their herd, but no reds, Davis herd in the US has black, and no reds, (large herd closed since the 60's), and the Bedford herd in the US has only black animals. There are likely other examples. These three herds linebreed and still no red animals.
On the other hand, it seems to me that where there are animals whose pedigrees have been questioned, (introgression), red pops out here and there.
One good example is Parndon Charley Pudding. When he was bred to purebred animals, he threw black calves. ( There was one recorded red, but I am not sure of the pedigree background of that breeding). When he was bred to the appendix animals in the Templeton herd, he threw all red animals. ( See the UK herdbooks from the mid to late 1960's.)
In the US, it is said, there were no more reds than the fingers on one hand until the importation of red bulls in the mid 1980's, and the pedigree/genetics of those bulls have been controversial.
This would make a great research project for a genetic student!
On the other hand, it seems to me that where there are animals whose pedigrees have been questioned, (introgression), red pops out here and there.
One good example is Parndon Charley Pudding. When he was bred to purebred animals, he threw black calves. ( There was one recorded red, but I am not sure of the pedigree background of that breeding). When he was bred to the appendix animals in the Templeton herd, he threw all red animals. ( See the UK herdbooks from the mid to late 1960's.)
In the US, it is said, there were no more reds than the fingers on one hand until the importation of red bulls in the mid 1980's, and the pedigree/genetics of those bulls have been controversial.
This would make a great research project for a genetic student!
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Duncan MacIntyre
- Posts: 2372
- Joined: Tue Mar 30, 2004 12:38 am
- Location: Isle of Bute, Scotland, UK
If a herd with 100 cows has one cow carrying red, and the other homozygous black, uses homogous black bulls for 100 years and keeps all the heifers, as long as they are bred to homozygous black bulls no red will show. But if the one heterozygous black/red is bred to a red bull then 50% of the calves will be red. If a black bull heterozygous black/red is used on such a female then 25% will be red, and 50% will carry red but not show it. If the red gene is present but at a very low incidence, then it can carry on for ever unseen till it meets another partner carrying red. Red has been recorded in dexters since the earliest efforts at recording pedigrees, so there is no mystery as to where some red came from. I know that red may well have been introduced by grading up but that is a different issue and does not cast any doubt on the origin - it is all there in the records. In the first Dublin herdbook one heifer is recorded as "White with a little red" so why do we get so worked up??
The dun colour which showed in the Woodmagic herd has been examined by professional geneticists and seems to be unique, quite different to the dun seen in Galloways and other breeds of cattle. It does seem to work in a different way to red and dun animals will carry black but it seems they may also carry hidden red. With an inbreeding programme in place in my small herd in a few years I may well have evidence of that.
Duncan
The dun colour which showed in the Woodmagic herd has been examined by professional geneticists and seems to be unique, quite different to the dun seen in Galloways and other breeds of cattle. It does seem to work in a different way to red and dun animals will carry black but it seems they may also carry hidden red. With an inbreeding programme in place in my small herd in a few years I may well have evidence of that.
Duncan
Duncan MacIntyre
Burnside Dexters 00316
Burnside
Ascog
Isle of Bute
Burnside Dexters 00316
Burnside
Ascog
Isle of Bute