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Pigeon racing is a worldwide popular sport where pigeons are placed away from home in order to find their way back. Characteristics such as navigation, speed and spatial memory are crucial abilities which demand the highest possible level for a pigeon to survive the journey. Pigeons who have a navigational system developed to find their way home are classified as homing pigeons. Racing pigeons are homing pigeons precisely selected and bred to find their way home in the shortest time possible. Several genes involved in processes such as metabolism regulation, neuronal signaling and sight are confirmed to be involved in their success of returning home according to the travel distance. However, pigeon races can be up to 1000 km long which is significantly longer compared to the distance pigeons travel outside of race. As a consequence, a high number of pigeons are lost during the race or die of exhaustion. Therefore, genetic testing of racing pigeons or pigeons whose offspring is intended for racing is extremely important. Optimal results provide significantly higher guarantee of pigeon successfully finishing the race, without getting lost or hurt. Genes of interest for testing prior to the race are those who have influence on either survivability or ability to successfully locate their home lofts. 1
Sample type: A biological sample needs to be obtained from an animal of interest in order to use our service. For pigeons, the sample should be feathers or blood which is non-coagulated and in a test tube containing EDTA. While taking a sample, please be aware that contamination needs to be avoided as much as possible, especially if you are taking samples from different animals at the same time. After the sample is taken, fill out the appropriate order form with basic information about your animal and needed tests (https://www.animalabs.com/2021/order-forms/).
LDHA is an isoform of lactate dehydrogenase specifically found in muscle tissue where it is responsible for synthesis as well as recycling of lactate. Lactate is a byproduct made in muscles usually during intensive workout, it causes sore muscles and can lead to tissue damage. It plays an important role in anaerobic metabolism which impacts pigeon endurance during the flight.2 In addition, lactate is important in forming spatial working memory.3 Research among the best performing pigeons found that specific mutation of LDHA gene showed better performance. Following that, LDHA soon began to be known as the "speed gene". LDHA is coded by two genes whose variations are called alleles. There are 2 different alleles that can be found coding LDHA protein. Those alleles are A and B allele giving possibilities of 3 different genotypes: AA, AB and BB. LDHA analysis among the best racing pigeons showed that A allele is found among top performers with the genotype AB being the most represented. Although, pigeons with BB genotype are also found among best performers. In conclusion, mutation in LDHA gene is not necessary but rather a preference for the best racing performance. However, among pigeons whose race is 300-700 km long, we strongly reccommend testing for this mutation. The biggest effect of lactate can be seen during a flight that has to rely on anaerobic metabolism, but is not long enough to rely on aerobic metabolism which is when this mutation has the biggest effect. 4
The mesolimbic system, which is responsible for complex behaviour and personality traits, is highly regulated by dopamine receptors.5 Gene for dopamine receptor type 4 (DRD4) was analysed among pigeons during short and long races in order to determine its effect on flight performance. Two variations of this gene are known as DRD4a and DRD4b defined by presence of cytosine in specific sequence position. If those places acquire specific mutations, pigeons can achieve better performance during races. Both mutations include the change from cytosine to thymine, and therefore, possible genotypes for DRD4a and DRD4b respectively are CC (wild type with no gain in speed), CT (better performance during short races) and TT (generally better performance). In conclusion, mutated DRD4 gene causes better performance, which is for heterozygous statistically significant in short races and in mutated homozygous statistically significant for all racing distances. We offer a service for testing both sequence positions which, if both are mutated, can significantly improve pigeons performance or be a useful input prior to breeding.6
During homing, pigeons, like many other birds, use magnetic field lines for their orientation. The mechanism of using magnetoreception for orientation during flight is still not known. However, research from 2021 found a relationship between cryptochromes, proteins in pigeons' retina, and racing performance during short distances. Sequencing of cryptochrome 1 (CRY1) found a polymorphism which gave better results in 100 - 400 km flight. Pigeons had the best results when they were heterozygous, meaning they have a mutated and non-mutated allele at the same time. This mutation can improve pigeons navigational ability and, therefore, make them more capable of navigating to their loft which is specifically important if weather conditions and flight path are not optimal. 7
More than 60% of birds worldwide are monomorphic meaning that determination of sex is not possible through physical features. Sex determination in domestic pigeons is impossible through their physical appearance, so genetic testing needs to be done. Sex determination in birds is done by detecting genes specific for each of the sex chromosomes. Unlike humans, sex in birds is determined by chromosomes Z and W, where females are heteromorphic (ZW) and males are homomorphic (ZZ). There are two genes conserved on sex chromosomes, CHD-Z on Z chromosome, and CHD-W on W chromosome. Therefore, PCR can easily be done in order to determine the sex of the bird. Males will have amplicons only for CHD-Z, in contrast to females, who have both genes. Determining a pigeon’s sex based on the presence of testicles can only be done post-mortem. In contrast, genetic testing offers painless and reliable results within a short period of time.8
DNA represents the genetic identity of every individual. However, sequencing the entirety of an individual's DNA would be difficult and long-lasting work. On the other hand, along the DNA molecule there are sequences with repetitive DNA motifs which are unique for every individual. DNA profiling is the process of determining those motifs (also called short tandem repeats or STRs). By doing this test, a pigeon gets its "genetic identity card", which can be used for registration purposes, parentage confirmation or as identity evidence if a pigeon has been stolen, hurt or lost. In order for the test to be reliable and valid, at least 6 different markers must be used. 9 Our service uses a scientifically and statistically proven panel of markers obtained by International Society of Animal Genetics (ISAG). This panel is composed of 16 STR loci: PIGN15, PIGN10, PIGN57, PIGN26, CliμD16, CliμD19, PIGN12, CliμD17, CliμT17, PIGN04, CliμD01, CliμD11, CliμD35, CliμT02, CliμT13 and CliμT43. DNA profiling offers results with an accuracy higher than 99,99%. 10
If pigeon breeding is not under strict control, doubt and uncertainty about the sire of an offspring is a common case. This usually happens because breeding mates are not kept inside separate boxes and, in addition, determination of males and females by their physical features is not possible. Parentage determination is, just like DNA profiling, done with STR analysis. In this case, results of an offspring need to be precisely analysed along with DNA of a dam and sire. In the offspring, the number of repeats inside the tested microsatellites will be a combination of repeats of the dam and sire. Hence it is important to send samples from both parents in order for results to be valid with 100% certainty. In addition, parentage determination is, at the same time, the result of some other genetic tests according to the results of the dam and sire. For example, if the dam has been tested before and she is determined as homozygous wild type for a certain recessive disease, we can already know that the offspring is of a wild type phenotype too, and no further genetic testing will be needed.
Note: If interested, the principles of inheritance in case of dominant and recessive diseases is explained in the paragraph "Importance of genetic testing" inside the category "Horse genetic diseases".