Genetic selection for udder health is often based on the indicator trait somatic cell score (SCS), which is correlated with clinical mastitis and has a moderate heritability. We used combined linkage and linkage disequilibrium analysis to refine mapping of a previously reported quantitative trait locus (QTL) affecting SCS on Bos taurus autosome 27 (BTA27) in the German Holstein population. A granddaughter design of six grandsire families with 492 sons progeny tested for an average of 190 daughters per son was investigated. Nineteen microsatellite markers were genotyped along a segment of 26.2 cM proximally on BTA27. A chromosome-wide significant QTL was identified between DIK2879 and KIBS272 using combined analysis. The region of interest for future fine mapping experiments was narrowed to the marker interval KIBS272-DIK2191 with a confidence interval of 3.27 cM. The QTL was estimated to be responsible for 18% of the genetic variation in SCS. Application of a 2-QTL model did not result in higher test statistics. Animals likely to be heterozygous or homozygous at the QTL were identified. This study provides a basis for the selection of further markers in linkage disequilibrium with the QTL affecting SCS on BTA27. Key words: Fine-mapping, mastitis, BTA27, somatic cell score, Holstein
Identification of a two-marker-haplotype on Bos taurus autosome 18 associated with somatic cell score in German Holstein cattle
