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Supernumeraries in Racing Homer

by Koen Joris (B) and Axel Sell (D)

 Speaking about supernumeraries we  often get from breeders the opinion that pigeons with 11 primaries or more have advantages in the competition against those with 10 primaries (wild-type) only. So recently in a report in the journal 'Die Brieftaube' no. 44 of 2016. About the genetics of the phenomenon there was long speculation only. The perhaps most famous pigeon book in the world, 'The Pigeon' by Wendell M. Levi, assumes a dominant inheritance. Perhaps because occasionally some young with this characteristic were raised from such a parent. For breeders who want to either increase the number of supernumeraries in their strain or even want to get rid of them, the results of a recent study will be of interest.

Fig. 1: Supernumerary Racing Homer (Photo: Koen Joris)

Dominant or recessive? In the case of unknown phenomena, this is often the first question. If it would be a dominant feature we would get from a heterozygous individual 50% offspring with that feature. If only 5 or 6 young are raised and none with that feature, then this could be traced back to chance. If 1 or 2 with that feature are raised, then one will feel confirmed in his expectation. However, the same result can also be expected with a recessive feature. If an individual with one recessive trait is mated with another without the respective factor in the genome, then you will not get any young with the trait. If it is accidentally mated with a (recessive) carrier of the gene, then 50% of the offspring show the trait. A recessive characteristic for supernumeraries often is assumed from breeders who occasionally, got an 11-penner in strains where the other pigeons had only the typical 10 primaries.

Koen Joris was probably the first who did extensive tests. He had introduced in his loft an 11-penner, which with different hens raised only young of the wild-type. In the subsequent generations and after the addition of further 11-penners from other lofts, one- and two-sided 11-penners were no longer a rarity. From 24 couples of supernumeraries x wild-type 143 young were raised and 35 or 24% from them were supernumeraries. For a dominant feature, it should have been about 50%. With this large number, the deviation can no longer be traced back to coincidence. The thesis of dominance at Levi could thus be regarded as disproved.

 

Couples

Youngsters

Supernumeraries

per cent

Supernumerary cock x Wild-Type hen

17

109

27

25

Wild-Type cock x Supernumerary hen

7

34

8

24

Total

24

143

35

24

 Table 1: Supernumerary x Wild-Type und vice versa

It is not yet a refutation for the thesis of a recessive feature. Because one could not assume that all the phenotypical wild-type used as a test partner were carrier of the recessive trait. Less than 50% were therefore expected with a recessive feature. The thesis, however, could be excluded by the following test series. First 13 couples of supernumeraries mated with each other produced 71 young and 22 (or 31%) of them phenotypical the wild-type with 10 primaries. In a simple recessive inheritance it would have been none.

 

couples

youngsters

Wild-Type

per cent

Supernumerary x Supernumerary Groupe 1

7

34

0

0

Supernumerary x Supernumerary Groupe 2

6

37

22

59

Total

13

71

22

31

 Table 2: Supernumerary x Supernumerary

The test was supplemented by mating some of the young produced from supernumerary couples with each other or with their supernumerary parents (Table 3).

 

couples

youngsters

Wild-Type

per cent

Supernumerary raised from supernumeraries mated with each other

3

22

3

14

Supernumerary cock raised from supernumeraries x supernumerary hen

2

14

8

57

Supernumerary cock x supernumerary raised from supernumeraries

4

32

6

19

Total

9

68

17

25

 Table 3: Supernumeraries with different background mated with each other

At the first test summarized in Table 2 it is striking that 7 of the couples raised only supernumeraries, while 6 had a significantly higher proportion of normal ones than those 24% of all 13 couples together. This indicated a different genetic endowment of the sub-groups. Some of the supernumeraries appeared to be only heterozygous with one or several of the factors involved. It was therefore necessary to look for explanations beyond the simple text book Mendelian model of heredity. Thus, e.g. in human genetics, a better understanding of  more complex phenomena is attained by modeling the interaction of several genes. Certain genes can only have an effect  if certain genes are present on one or more other gene-loci. If they are not present, the trait remains covered. One speaks of epistatic relationships (Cordell, 2002).

Following the investigation in the strain of racing homers, test mating were carried out in single boxes by mating some of the supernumeraries with Gimpel Pigeons. Those were from a stock in which supernumeraries were not observed so far. Following the idea of epistatic relations the best statistical fit was derived for a model of the interaction of three factors sn1, sn2 and sn3. In combination it seems to be sufficient  if one of them is present in heterozygosity only. Thus, the first generation (F1) consisted of young with 10 primaries. 130 young of the F2 were raised from three couples of the first generation mated together over several years. From the F2 only 8 (6.2%) were supernumeraries.

couples

youngsters

supernumeraries

per cent

no. 1

48

2

4,2%

no. 2

48

3

6,3%

no. 3

34

3

8,8%

total

130

8

6,2%

Table 4: F2 from gimpel-homer crosses

Finally, 5 of the F1 were mated back to supernumeraries  of the homer stock and produced 12 (20%) from 60 offspring. From all 5 couples at least one supernumerary was raised. The percentages, however, were different.

couples

youngsters

supernumeraries

per cent

no. 1

27

2

7,4

no. 2

8

2

25,0

no. 3

10

1

10,0

no. 4

8

6

75,0

Nr. 5

7

1

14,3

total

60

12

20,0

 Table 5: Backcross of the F1 from supernumerary homer x gimpel pigeon cross to supernumerary homers

Fig. 2: Backcross supernumerary from Racing Homer x Gimpel Pigeon cross to supernumerary Racing Homer (Photo: Koen Joris)

More insight will perhaps be gained in other ways with the advances of molecular genetics. It is hard to imagine, though it would be desirable that someone  will increase the observation base with conventional pairings. For practical breeding the results mean that it is easily possible by selection to increase the number of supernumeraries in a strain and also to breed them true. However, the introduction of a pigeon with 10 primaries perhaps to stabilize performance of the strain would be a serious setback for this goal. On the other hand, breeders, who want to permanently eliminate this trait from their stock, should not use any supernumeraire in breeding. The direct offspring will not have the characteristic, but it will reappear in subsequent generations.

Literature:

Cordell, Heather J., Epistasis: what it means, what it doesn't mean, and statistical methods to detect it in humans, Human Molecular Genetics, 2002, Vol. 11, No. 20, pp. 2463-2468.

Joris, Koen and Axel Sell, Überschwingigkeit bei Haustauben, RÖK Freude mit Kleintierzucht, January 2017, pp. 8-11.

 Levi, Wendell M., The Pigeon, 1. ed. 1941, reprinted with changes and additions 1963, reprinted 1969, Levi Publishing Company, Sumter. 

Sell, Axel, Brieftauben und ihre Verwandten, Achim 2014.

Sell, Axel, Pigeon Genetics, Applied Genetics in the Domestic Pigeon, Achim 2012.