From a friend of mine.
"A friend of mine did get his breeders typed but it escapes me what good it would do to know the genotype regarding that one gene. Here is what it says:
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The A allele is a rare variation, found in less then 12% of normal racing pigeons and less then 1% of pigeons had the statisticlly more favorable AA genotype. It is important to mention that some top racing pigeons are BB genotype meaning that the A allele is not absolutely necessary to be able to perform at a high level. This suggests that additional genes are involved in race performance including speed and distance.
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As I read it, it says that some top racing pigeons carry the B allele and other top racing pigeons carry the A allele, both alleles are types of one of very many genes coding for enzymes needed during carbohydrate metabolism but all of us know by now that the most important fuel for flying is fat and not carbohydrates. So knowing the genotype regarding this one gene would be pretty useless IMHO."