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The LDHA Gene

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Site last updated on 9/16/17

Recently published scientific papers have reported that the A allele of the LDHA gene may be associated with superior racing performance.

How does it work? Like any subject, the more you understand the underlying details, the better you understand the big picture. I discuss the subject in more detail in the book, but here are the salient points which should give you enough information to have a working understanding:

  • When animals exercise vigorously enough that they incur an oxygen deficit, their muscle cells use an alternative metabolic pathway that does not require oxygen to produce energy. One of the products of this anaerobic respiration pathway is lactic acid (which dissociates into lactate (a negative ion) and a positive hydrogen ion).
  • For many years it was thought that the build up of lactic acid in muscle cells during sustained or intense exercise, caused the fatigue that eventually sets in. Today we know it isn't quite that simple. There are many complex processes that are involved.
  • Lactate Dehydrogenase (LDH) is an enzyme that is involved in the breakdown of lactate to pyruvate (and the reverse reaction of pyruvate to lactate. The gene that codes for LDH in muscle cells is the LDHA gene (the LDH that is active in cardiac tissue is coded for by the LDHB gene; there are additional forms of LDH in other tissue types).
  • Two different alleles have been found in pigeons for the LDHA gene, A and B. This means the possible genotypes for LDHA in pigeons are BB, AB and AA.
  • Research papers have been published which suggest that birds with the A allele have statistically better race performance than birds without the A allele. Presumably, birds of genotype AA and AB produce a form of Lactate Dehydrogenase that is better able to utilize and/or manage lactate levels in muscle cells during strenuous exercise than the form found in birds of the BB genotype.
  • The LDHA genotype can be determined by a DNA test that is available from a number of laboratories.
  • The gene is not sex linked and so the possible matings will produce these results:
    • BB x BB produces 100% BB
    • AB x BB produces 50% BB and 50% AB
    • AB x AB produced 25% AA, 50% AB and 25% BB
    • AA x AA produces 100% AA
  • While it will take time to get there, the idea is that flocks whose breeders are AA will be able to consistently produce birds that are superior racers to flocks whose breeders are BB or largely BB (all other factors being the same).

There are some vital points that need to be understood when considering the role of the LDHA gene in racing pigeons:

  • This is not the only gene that affects racing performance. It is very likely an important one, but it is NOT the whole story. Anyone thinking this is the “magic bullet” that trumps everything else, is just setting themselves up for a huge disappointment. My estimation is that there are at least 100 different genes that contribute to racing performance and this is just one (albeit one of the more important ones). Let me give a couple of examples.
    • My best young bird this season (2015) was DNA tested for the LDHA gene and the test showed that it was BB and so it did not carry the A allele.
    • My two best young birds in 2013 were full brothers, 3045 and 3098. They were both outstanding, but 3045 was a little better. They were also my best two old birds in 2014 and again, 3045 was just a little better than 3098. Both were DNA tested and 3045 does NOT carry the A allele (he is BB)  and 3098 does (he is AB).
    • I work closely with Hapyco Lofts of California. We tested several of their birds including the cock that Chic Brooks considers the best breeder he has ever owned, having produced more winners and top performers than he can keep track of. You guessed it, the bird tested negative for the A allele (he was BB).
       
  • So with examples like these, why are we even having this discussion? There are two reasons.
  • First, while it isn't the whole story, the LDHA gene may be one of the most significant genes affecting race performance. Lets look at a summary of the research findings:

    • The first paper was published in 2006 in the Journal of Applied Genetics, February 2006, 47(1):63-6, “Polymorphism within the LDHA gene in the homing and non-homing pigeons“ by Andrzej Dybus, Jacek Pijanka, Yeong-Hsiang Cheng, Fangmiin Sheen, Wilhelm Grzesiak and Magdalena Muszyriska. It showed that racing performance in pigeons is positively influenced by the presence of the A allele:
      • 445 pigeons were DNA tested for the LDHA gene.
      • 79 of these pigeons were fancy birds and not racing birds (so presumably they had never been selected for racing performance). None of these birds were AA, 1.3% were AB and 98.7% were BB.(This makes the frequency of the A allele for non racing breeds of pigeons  0.6%).
      • 145 of the pigeons tested were a control group, meaning they were a population of racing birds that had not been prescreened for the research study on the basis of racing performances. They were taken from a university loft in Poland. 0.7% of these were AA, 11.7% were AB, 87.6% were BB. (This makes the frequency of the A allele for average racing pigeons 6.5%).The ten fold higher frequency of the A allele in this group compared to non racing breeds suggests that years of breeder’s selection based on race results has resulted in the selection for the LDHA A allele.
      • A third group of 98 birds consisted of “top racing pigeons” selected from lofts in Poland. 3.3% of these were AA, 34.1% were AB, 62.6% were BB. (This makes the frequency of the A allele for top racing pigeons in Poland 20.3%).
      • A fourth group of 123 birds consisted of “top racing pigeons” selected from lofts in China and Taiwan. 9.2% of these were AA,  25.5% were AB, and 65.3% were BB. (This makes the frequency of the A allele for top racing pigeons in China and Taiwan 21.9%).
         
    • The second paper was published in 2014 in Japan Poultry Science, March 2014, 51: 364-368, “Single Nucleotide Polymorphism in the LDHA Gene as a Potential Marker for the Racing Performance of Pigeons” by Witold S.Proskura, Daria Cicho, Wilhelm Grzesiak, Daniel Zaborski, Ewa Sell-Kubiak, Yeong-Hsiang Cheng and Andrzej Dybus. This research effort more carefully measured race performance than the work done in the above paper. This paper confirmed racing performance in pigeons is positively influenced by the presence of the A allele, but it also raised the possibility that the influence of AA may exceed that of AB in races under 250 miles and that the A allele may be less important in the distance races. More research and data is needed on these later points:
      • 123 pigeons (60 hens and 63 cocks) from two racing lofts in Poland were each raced a full season on widowhood against section members (the paper did not make it clear if the season was young birds or old birds, but the use of widowhood and the distances of the races suggests it was old birds).
      • There were eight short races (less than 400 km (249 miles)) and six long races (greater than 500 km (311 miles)). A total of 1380 race records were studied. This represents 80% of the number possible if all birds went to all races (123 birds x 14 races = 1722 potential race records).
      • Racing performance was measured using a formula that only gave points to birds placing in the top 20% of all birds in the race (from all lofts in the race, not just the two in the study). The bird placing 1st received 100 points. The other placings were associated with decreasing points. This is the formula that was used:
        • AP = ((a - b + 1)/a)*100 where
               AP = ace points
               a = the number of birds placing in the top 20%
               p = the bird’s place

      • The mean AP for all races for BB birds was 29.96 , AB birds was 37.02 and AA birds was 37.70. The results showed a statistically significant difference between the results for the BB birds and the AB/AA birds.
      • The mean AP for short races for BB birds was 29.44 , AB birds was 37.23 and AA birds was 46.52. The results showed a statistically significant difference between the results for the BB birds and the AB/AA birds. The differences between the AA and AB were not statistically significant, but given the small sample size of the AA birds (10 race records met this condition), this result merits a second look with a larger AA sample size.
      • The mean AP for long races for BB birds was 30.45 , AB birds was 36.83 and AA birds was 27.90. The results DID NOT show any statistically significant difference between the results for the BB, AB or AA  birds, suggesting that other genes may be more important than LDHA in distance races. Again, more research is needed.
         

    Second, DNA testing allows us to absolutely know the genotype of any bird we test and so it is possible for the astute breeder to get to the point where all of their breeders only carry the A allele. Having “fixed” this trait into their loft, they could continue their improvement through the selection of other key genes that influence racing performance.

  • Much more research needs to be conducted on this subject before we can safely conclude we understand how the LDHA gene is impacting race performance. The results reported to date though are sufficiently intriguing to me that I believe it makes sense to DNA test our breeders and to begin working toward a breeding flock that is homozygous for the A allele.
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