[Genetic defects in Braunvieh cattle of Switzerland - an overview]

Since 2010, genomic selection in Swiss cattle breeding has led to significant progress in the two local Braunvieh populations, Brown Swiss and Original Braunvieh. However, it has also contributed to further inbreeding, leading to an increased risk of outbreaks of monogenic recessive defects. Some long-known inherited diseases such as arachnomelia, spinal muscular atrophy, spinal dysmyelination, Weaver syndrome and renal dysplasia are now of little clinical importance, while new haplotypes and gene variants associated with reproductive disorders have recently been described. These include so-called fertility haplotypes and genetic diseases that rarely or never occur homozygous because the affected animals die shortly after birth or early in pregnancy. This work provides an overview of the known recessive genetic defects in Swiss Braunvieh cattle. Data from 56, 000 Swiss breeding cattle on 12 genetic defects show that known inherited diseases in Braunvieh only occur very sporadically (defect allele frequency < 1 %). Only the recently described achromatopsia (Original Braunvieh haplotype 1) has a relevant defect allele frequency of over 7 % and should be taken into account for mating plans in order to avoid calves with day blindness. In addition, the Braunvieh haplotypes 6 and 14 and the Original Braunvieh haplotypes 4 and 9 occur between 2-6 % and the mating of heterozygous carriers should be avoided in order to avoid homozygous offsprings that are presumably not embryonically viable. The further spread of known genetic defects can be prevented through comprehensive genotyping of the breeding populations and the careful selection of breeding animals, recently also with the help of digital apps for mating planning. Thus, genetically caused reproductive losses or the number of affected animals can be reduced, animal health and welfare can be sustainably improved through selective breeding.