Polled
When polled individuals are called in usually horned mammals (eg. As cattle , sheep , goats ), which because of a genetic predisposition do not have horns.
This must be distinguished from animals that had horn systems that are lost through human or other influences. The deliberate removal of horns is called dehorning .
genetics
Hereditary polledness is particularly important in domestic goats , where it is associated with the appearance of hermaphrodites . The polled is a desirable feature because it can simplify the keeping of the animals. However, mating two polled animals can lead to disorders in the development of the phenotypic sex:
The allele for polled already in the heterozygous form leads to polled, so it is dominant over horned for polled. If the allele is present in homozygous form, depending on the karyotype , recessive malformations of the genital organs also occur:
- Genetically male goats (karyotype XY) that are homozygous for polledness are infertile in approximately 50% of cases.
- Genetically female goats (karyotype XX) that are homozygous for polled are always infertile. The following phenotypes are possible:
- male phenotype with hypoplastic testicles ("pseudobock")
- Hermaphrodite ("Zwicke", "Spritzbock")
- female phenotype, but sterile
literature
- Horst Kräusslich , Gottfried Brem: Animal breeding and general agriculture for veterinarians . Ferdinand Enke Verlag Stuttgart 1997, ISBN 3-432-26621-9 , p. 406 f.