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DNA testing: How many times is the pedigree correct?

Some statistics of DNA parentage testing

 

After having tested a lot of parentages by DNA, we thought it would be nice to publish some statistics of how many parentages were tested as correct parents or not. We have included 1241 recent parentage tests and 3617 samples for this evaluation, meaning we can make some very nice conclusions in general for racing pigeon breeding.

For these tests we assume that the percentage of deliberate wrong pedigrees (pedigree fraud) will be very small, as almost all requests were done by the pigeon breeders themselves. This means that the percentages of wrong parentages will be very accurate as being non-deliberate caused by cheating of a hen or cock or administration mistakes by the fancier him- or herself. Also a lot of the fanciers that requested the tests are professional or semi-professional pigeon racers, meaning we could assume that mistakes because of wrong administration will be less than the general pigeon fancier population. The testing itself is extremely reliable as 16 markers were tested (according to the international ISAG Pigeon Panel), meaning 32 different places on the genome (DNA) are tested and compared with the parents. Also when there is a deviation of markers the lab always retests a second sample and includes more markers when necessary. If both parents (but even if one parent) are tested the reliability approaches 100%. Other tests not according to ISAG f.e. tests with 8 markers and only one sample are not that reliable, meaning much more parentages would be tested as being "right" while the pedigree is in fact not correct; this will be especially the case if the testing would occur in a close or closely inbred family.

 

The numbers

 

6,77% of the parentage tests had a doubt of the parentage after testing of the first sample only mostly because of marker deviation, so without retests of the second sample and extra markers if needed. In some cases of bad sample quality there could also not be a first conclusion, but in 91,54% the parentage could be immediately concluded to be correct as the parents that were on the pedigree.
4,27% of the total of parentage tests was tested by DNA to be definitely wrong (after retests of second samples and extra markers); in 64,15% of these wrong cases only the father was wrong, in 26,42% both parents were wrong and in 9,4% only the mother was wrong. These numbers seem to be logical as we could except that cheating of a hen and/or cock will indeed make us see more mistakes with father parentage testing. Also it is known that male sperm can survive for a long time in the oviduct of a female pigeon, making it possible she could still be fertilized by a previous male. The mistakes of both parents are definitely caused more by administration mistakes (especially we see this when putting eggs under other couples); some people only write a name of a hen f.e. and not the ringnumber (f.e. daughter of "..." but the fancier has more daughters of this pigeon...). If it was possible and if the client had the urge to search for the real parents with extra tests, usually they were found. Of the 64,15% birds with wrong fathers in 20,59% we could find the real father; of the 26,42% with the parents being both wrong we could identify the real parents in 7,15% of the cases and of the 9,4% pigeons with a wrong mother in 40% we could find the real mother. This means in total in 18,86% of these wrong parentages we were able to find the real parents. This could seem small but this is actually the majority of the cases in which the client wanted to look for the real parents; in the majority of these wrong parentages the client didn't want or didn't ask to look further for the real parents.
In 1,5% of the total parentage tests there had been a mutation in the DNA, but could be concluded the parentage as correct. In every generation there are some mutations possible in the DNA strand, which is considered one of the main powers behind the evolution of species.


Some conclusions

 

Despite of the clearly good intentions of the pigeon fanciers which we could assume to be very high and reliable, we still do see a lot of wrong pedigrees. We ask ourselves serious questions how many pedigrees of pigeons sold without a good quality DNA testing, are actually correct. Even with completely assuming good intentions already 1 of 23 pigeon pedigrees are wrong on average. We can only guess for percentages when intentions of a seller are doubtful or when the fancier doesn't keep a good administration or even when the DNA testing is of low quality.
It is very clear that some fanciers do not make many mistakes and some make more (again clearly without bad intentions of fraud from what we expect). We also clearly see a difference in pigeon strains f.e. extreme long distance strains known to be raced more on nest system seem to be more 'loyal' to their partner. Off course open loft breeding gives more probability of wrong parentages.


New research on LDHA

 

In the mean time there is a new published scientific article on LDHA (see article on PIPA 2014), the scientific proved performance gene for racing pigeons (Proskura et al, The Journal of Poultry; March 25, 2014 ) . In this study 3 alleles of the LDHA gene were described including the preferred and very rare "A" allele, giving a clear advantage for racing performance (the original "B" allele was named "G" in this study). The genotypes of 123 pigeons on total widowhood system were compared with their capability of scoring high in the ace pigeon competition. Again clearly the pigeons with the "A" variant (AG or the extremely rare AA) scored significantly better on all races on averages and on all distances! The extremely rare AA pigeons scored the highest mean ace pigeon points, clearly validating the original hypothesis that this gene clearly has a strong influence on racing performance. In this study it was striking that the influence of this gene on ace points was even more on the sprint races under 400km than on the long races what we would not have expected from earlier research, but this number was within the standard deviation. So on all distances the influence was very clear. Also new in this study is the fact that AA scores better than AG (which in turn scores much better than GG). GG still is the most common genotype (80% of the pigeons).
The article also raises the question on what could be the reason for this clear influence on racing capabilities, indicating the hypothesis it could be important for the gene expression of LDHA or even a linkage with another gene on the same chromosome. This still requires more in-depth investigation.


Ruben Lanckriet
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