Gonadal hypoplasia in Swedish Mountain cattle and other native Swedish cattle breeds

Abstract: The Swedish Mountain cattle and several related breeds show the phenotype of colour-sidedness. The genetic reasons for this phenotype are a translocation and duplication from chr6 to chr29 (known as Cs29) including the KIT gene and an additional translocation with part of the Cs29 translocation from chr29 back to chr6 (Cs6). Besides the colour-sidedness the Cs29 translocation is known to be responsible for gonadal hypoplasia. Gonadal hypoplasia leads to an underdevelopment of the ovaries and testicles and can cause fertility problems. Breeders of the Swedish Mountain cattle have been aware of the appearance of gonadal hypoplasia since the early 20th century and have been trying to select against it ever since. However, there are still individuals found which show gonadal hypoplasia. Therefore, the aim of this research was to investigate, how common the allele that is responsible for gonadal hypoplasia is in Swedish Mountain cattle and closely related breeds based on DNA samples from individuals born between 1976 and 2015. Therefore, 60 DNA samples were analysed using three primer pairs to identify the different genotypes of the Cs29 translocation and the additional Cs6 translocation. The PCR was done using a multiplex of the primer pairs and the genotypes were identified by doing an electrophoresis in TapeStation. The estimated allele frequencies for the Cs29 translocation were 0.22 for Swedish Polled, 0.27 for Fjällnära, 0.40 for Väneko, 0.56 for Bohus Polled and 0.57 for Swedish Mountain cattle. The results indicate that the Cs29 translocation, responsible for gonadal hypoplasia, is still common in Swedish Mountain cattle and can also be found in related breeds and other native Swedish cattle breeds that show the colour-sidedness phenotype. Thus, the integration of a DNA analysis to test for gonadal hypoplasia to detect the carriers of the Cs29 translocation would be favourable to increase the selection success against gonadal hypoplasia.