The project builds on the results of the PSOROVIS project in which (1) a phenotyping method has been established for mange susceptibility, (2) a first genome wide association study revealed a significant region on chromosome 11 and (3) an indication was found that the nt821 (dell) MSTN mutation causing double muscling in the Belgian Blue (BB) cattle is linked to the increased mange susceptibility. These preliminary results should be verified before a genetic test can be used in practice. More precisely, the following research questions need to be addressed:

1. Can the QTL that was found on BTAll be confirmed in a larger sample of Belgian Blue cattle?
a. Can we identify a haplotype linked to mange susceptibility?
b. Which genes are underlying this QTL and can a causative mutation be identified using sequence based association?
c. If a causative mutation is found, can a (genomic) selection program be developed in which this is incorporated as a fixed effect?

2. Is it possible to set up a genomic selection strategy for a quantitative trait in a population based on a small training population in which the phenotype is considered as a binary trait (case/control)?

3. Can the phenotyping method be simplified as such that more animals can be sampled on a routine basis?

4. Can the association that was found in the PSOROVIS MSTN-study be confirmed in a second population?
a. Is the nt821 (del11) MSTN mutation that is causing double muscling in Belgian Blue cattle associated with mange susceptibility?

5. Is it possible to develop and validate a genetic test for Psoroptic mange susceptibility that can be used in the field?