A new Holstein Haplotype affecting calf survival

Abstract

In recent years, the availability of phenotypic records and genomic data for cattle and the application of genomic tools revealed haplotypes affecting fertility and prenatal death. This study reports the identification of a new haplotype associated with calf survival in the Holstein population. Several calves from specific mating initially showed unspecific symptoms like chronic diarrhea and insufficient development. Affected animals died within the first months of life despite of symptomatic treatment. A genome-wide case-control-study based on 54K SNP Chip genotypes determined a causal region at BTA 11. Subsequent homozygosity mapping identified a haplotype affecting calf mortality in the homozygous state. Blood chemical analysis of affected calves revealed pronounced hypocholesterolemia indicating a disorder of the fat metabolism. Heterozygous animals without clinical manifestations show decreased levels of blood cholesterol suggesting a codominant inheritance for this genetic defect. Pedigree analyses revealed a prominent Canadian Holstein bull; MAUGHLIN STORM, as a carrier for this disorder. The widespread use of this bull and of its sons in the breeding program lead to a strong increase of the haplotype frequency in the German Holstein population within the last years. The occurrence of an identical healthy haplotype and the presence of several gaps within the bovine genome complicate the identification of a concordant variant.