MASTITIS RESISTANCE New breeding tools for improving mastitis resistance in European dairy cattle QLK5-CT

Mastitis the most common disease in dairy cattle (up to 40%) low heritability difficult to improve by selection veterinary records available only in few countries

SCC m m r%, v% m SCC vmvm m, v% r% UT SCC v%, v, m r, r% UT v%,SCC UT,SCC v% m UT, m SCC m, SCC v% m, v r% SCC m, v SCC m, v SCC UT Finnish Ayrshire genome scan results

Objectives zCombine different genome scans into a multi- population, multiple trait analysis

Objectives zCombine different genome scans into a multi- population, multiple trait analysis zImprove statistical methodology for fine-mapping

Objectives zCombine different genome scans into a multi- population, multiple trait analysis zImprove statistical methodology for fine-mapping zIdentify marker haplotypes associated with specific QTL alleles

Objectives zCombine different genome scans into a multi- population, multiple trait analysis zImprove statistical methodology for fine-mapping zIdentify marker haplotypes associated with specific QTL alleles  Dissect the genetic basis of mastitis resistance by analysis of: (i) disease etiology correlated to specific QTL alleles and pathogens, (ii) positional candidate gene sequence variation, and (iii) pleiotropic effects of each QTL

Material families included in Nordic QTL scans DYDs for clinical mastitis and somatic cell count (1st lact.) pathogen data of milk samples bovine RH-panel and BAC libraries from Roslin (COMRAD)

Fine-mapping zGenotyping of dense marker maps. The most significant chromosome areas are genotyped in segregating families with the produced marker panels zStatistical analyses. By developed multiple trait LD/ linkage mapping methodology (including longitudinal data)

Genetic dissection zPathogen specificity of QTL alleles. Daughter groups with known paternal QTL genotypes analysed for association (of pathogen)

Genetic dissection zPathogen specificity of QTL alleles. Daughter groups with known paternal QTL genotypes analysed for association (of pathogen) zAssociation of candidate gene variants with disease status.

Genetic dissection zPathogen specificity of QTL alleles. Daughter groups with known paternal QTL genotypes analysed for association (of pathogen) zAssociation of candidate gene variants with disease status. zAnalysis of pleiotropic effects on other traits -> strategy for use

New statistical methodology  statistical methods for fine-mapping QTL with LD/linkage mapping using information on multiple traits and longitudinal data zstatistical tool for marker assisted introgression of favourable QTL alleles to new breeds

Tools for genetic improvement zQTL allele haplotypes affecting clinical mastitis and/or somatic cell count will be mapped sufficiently precisely to be: (i) used with confidence for marker assisted selection within a breed; and (ii) used for marker assisted introgression between breeds.

Basis for further studies zA list of candidate genes, based on their position, including partial knowledge of sequence variation (SNPs). zKnowledge of association / non-association of candidate genes with mastitis resistance zKnowledge of differences in pathogen specificity of identified QTL alleles.

Strategy for use zKnowledge of the pleiotropic effects of each QTL on other economically important traits can be used to provide a strategy for the use of these QTL in breeding programs.

Research teams z MTT (Finland)/Johanna Vilkki z SLU (Sweden)/ Lena Andersson-Eklund z EAU (Estonia)/ Haldja Viinalass z DIAS (Denmark)/ Mogens Sando Lund z ROSLIN (UK)/ John Williams z ID-Lelystad (NL)/ Lucia Kaal