Posted: Fri Nov 17, 2006 1:34 am
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
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