One or more posts recently have touched the thorny problem of pedigrees suspected of being incorrect, and we frequently look a bit askance at graded up animals.
Should we?
The two things are of course very different. Grading up was allowed when the numbers of purebred animals was very low and the use of a grading up system allowed the breed to increase at a greater rate than a closed herdbook would have, and to do that without becoming too inbred. I feel very strongly that what has been allowed in by a legitimate breed society rule in the past, cannot now be rejected.
Mistaken pedigrees on the other hand have a sense of "I have been cheated" about them. If any of us were to be sold an animal where the sire turned out not to be a Dexter we would be quite justified in feeling cheated. We should remember that such things are relatively rare, and that in the majority of cases the breeder is unaware of the mistake rather than perpetrating a deliberate fraud.
At the end of the day the effect of both the grading up by allowed schemes and the occasional mistake is the same. We need to remember that the influence of the new genes halves with every generation, so if parent is another breed, the animal is 50% non-dexter,if the parent is a cross, the animal is 25% non-dexter, grandparent,it goes to 12.5% so by the time we get to 6 generations down the line the influence is around 1%. And we should not imagine that an Aberdeen Angus, for example, has genes which are 100% different from a Dexter. Any bovine in fact, no matter how different it may seem, will share the vast majority of the genes with any other bovine. The few which are different of course are usually the ones which make the breed characters different.
If I calculate, for example, the percentage of an alleged wrong sire of Godstone Esmiralda to my crop of calves this year who have her in their distant ancestry, I have Burnside Filmstar with about 1% influence, and Burnside Foreman with just 0.5%. It just happens, of course, that one gene which is easy to spot is the polling gene. The others in the half percent were likely to be shared genes with all other cattle in the first place.
We should also be aware that other factors may mean that the influence is not just a simple calculation - if I follow other lines in my breeding, where related individuals both with the same graded up ancestor are used, there will be a slight increase in influence - eg in the offspring of Burnside Challenger and Burnside Candytuft, the influence of Vycanny Orphan Annie, who was sired by a Polled Shorthorn, is half of the influence from each parent, ie .06% plus .12%, giving a massive 0.18% theoretical shorthorn. In fact both Candytuft and Challenger have lost the polled gene, not surprising when we get to the 8th and 9th generation.
So, why am I writing all this? Simply to try to point out that we need not worry about the breed becoming overwhelmed by foreign genes, and we certainly need not dismiss as grossly impure animals which have a tiny influence of some introduced breed be it deliberate or accidental, if that introduction occurred many generations ago.
Duncan
pedigree errors/graded up - getting introduced genes in perspective
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Duncan MacIntyre
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The difference between the graded up animal where the position can be ascertained, and one incorrectly registered, is that in the one case you know you are dealing with an unknown quantity. However, where the animal has been wrongly registered, and I agree the number is low, there is ignorance.
It has to be remembered that it is not a single gene but the thousands of others on the same chromosome, and all the other chromosomes from the unwanted breed that you may have collected.
Percentages and predictions will be variable and uncertain, you only need to compare two full sisters or brothers to realise it is all a gamble, in both cases they could share virtually no common genes. There can never be certainty that the undesirable genes have been dropped, even after five or six generations. In one case it will be lost in the third generation, in another it could be maintained for ten. It is this gamble that makes breeding so exciting, but I would prefer to know the odds.
It has to be remembered that it is not a single gene but the thousands of others on the same chromosome, and all the other chromosomes from the unwanted breed that you may have collected.
Percentages and predictions will be variable and uncertain, you only need to compare two full sisters or brothers to realise it is all a gamble, in both cases they could share virtually no common genes. There can never be certainty that the undesirable genes have been dropped, even after five or six generations. In one case it will be lost in the third generation, in another it could be maintained for ten. It is this gamble that makes breeding so exciting, but I would prefer to know the odds.
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Peter thornton
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- Joined: Mon Jun 21, 2004 4:41 pm
Whether we are talking about cattle or humans, DNA checks for everyone would produce many surprises!
I think that any breed of cattle probably has a great deal of accidental "grading up" over the years. Sometimes it is noticed and sometimes it is not. i.e. a bull gets over a fence (and sometimes it also gets back again) and providing the calf looks like the breed that is should be then the breeds gene pool has been expanded.
What I do find interesting is the results produced by breeders who work in more controlled conditions and where this kind of thing hardly ever happens. For example, pedigree dogs. What sometimes seems to ultimately result is an inbred annimal that may have all of the breed points but is not actually a very useful animal.
In other words, perhaps nature has a way of protecting us from ourselves. If we were all able to breed exactly the Dexter we wanted then we could end up with a perfect show animal that might be pretty useless as a cow.
Duncan, please tell me off if I'm talking B*&^&ks!
I think that any breed of cattle probably has a great deal of accidental "grading up" over the years. Sometimes it is noticed and sometimes it is not. i.e. a bull gets over a fence (and sometimes it also gets back again) and providing the calf looks like the breed that is should be then the breeds gene pool has been expanded.
What I do find interesting is the results produced by breeders who work in more controlled conditions and where this kind of thing hardly ever happens. For example, pedigree dogs. What sometimes seems to ultimately result is an inbred annimal that may have all of the breed points but is not actually a very useful animal.
In other words, perhaps nature has a way of protecting us from ourselves. If we were all able to breed exactly the Dexter we wanted then we could end up with a perfect show animal that might be pretty useless as a cow.
Duncan, please tell me off if I'm talking B*&^&ks!
In the case of cattle this is precisely why I favour the Dexter. Like the other rare breeds it has largely escaped the serious breeder. The commercial breeds have become milking machines, or lumps of beef for the plate. In the chase after economic priorities of the finished article, it has largely lost its ability to survive and thrive without being bolstered by drugs, medicine and artificial feeding.
Dog breeders are mostly driven by appearance and the show-ring, and I admit there have been efforts in that direction in the case of the Dexter, but the last 100 years has not negated all those many centuries that it was left to its own devices. Moreover the rapid turnover of breeders has prevented it. Personally my aim has simply been to perpetuate the best of what I inherited, not to ‘improve’ on it, to its detriment. Incidentally, I try to maintain only one working male out on the farm at any time.
Dog breeders are mostly driven by appearance and the show-ring, and I admit there have been efforts in that direction in the case of the Dexter, but the last 100 years has not negated all those many centuries that it was left to its own devices. Moreover the rapid turnover of breeders has prevented it. Personally my aim has simply been to perpetuate the best of what I inherited, not to ‘improve’ on it, to its detriment. Incidentally, I try to maintain only one working male out on the farm at any time.