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QTLs FOR SOMATIC CELL COUNTS IN DAIRY SHEEP Results from two QTL detection projects

QTLs FOR SOMATIC CELL COUNTS IN DAIRY SHEEP Results from two QTL detection projects Rachel Rupp, L. Schibler, E. Cribiu, Y. Amigues, M.Y. Boscher, L. Mura, T. Sechi, A. Fraghi, S. Casu, F. Barillet, A. Carta INRA, SAGA, Toulouse INRA, LGBC, Jouy en Josas LABOGENA, France

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QTLs FOR SOMATIC CELL COUNTS IN DAIRY SHEEP Results from two QTL detection projects

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  1. QTLs FOR SOMATIC CELL COUNTS IN DAIRY SHEEP Results from two QTL detection projects Rachel Rupp, L. Schibler, E. Cribiu, Y. Amigues, M.Y. Boscher, L. Mura, T. Sechi, A. Fraghi, S. Casu,F. Barillet,A. Carta INRA, SAGA, Toulouse INRA, LGBC, Jouy en Josas LABOGENA, France IZCS, Olmedo, Italy

  2. Mastitis: 11% Mastitis:24% Others Others Reproduction Milk production/age Why do we look for QTL for somatic cell counts in dairy sheep ? • Mastitis resistance = trait of increasing interest - Frequency Culling reasons in two French areas - Economic impact : culling, milk production, milk price… - Food safety and ‘image’

  3. Why do we look for QTL for somatic cell counts in dairy sheep ? • Polygenic variability of mastitis resistance Somatic Cell Counts in sheep milk • Predictor of udder infections • Early studies show genetic • variability: h²  0.12 • large scale recording and • genetic evaluation in France

  4. Why do we look for QTL for somatic cell counts in dairy sheep ? • To find newtools for selection (Marker/Gene Assisted Selection ?) • To better understand the biological basis of resistance to mastitis, predict long term selection effects, ….

  5. Two QTL detection projects

  6. Somatic Cell Counts Traits ? • 1 -Purebred GDD Lacaune design • LSCSEBVderegressed EBVs for repeated LSCS in L1-2 • 2 - Back-cross Sarda*Lacaune design • Single SCS= same trait repeatedwithin and across lactations (N=25571) • LSCSarithmetic mean of SCS /lactation • L1-L2-L3 Different trait across lactations • Rep Same trait repeated across lactations

  7. Results: QTLs for Somatic Cell Scores

  8. QTL for Somatic Cell Scores: OAR6=a common result in both designs

  9. QTL for Somatic Cell Scores: different results in the 2 designs Not investigated in the purebred GDD design Not found in the Sarda*Lacaune design

  10. Conclusion • QTL for SCC in dairy sheep exist • OAR6= found in both designs • Other results : OAR18, 16, 12, 13, 19 ? • No co segregation with production and morphology • Co segregtion with vacuometer measure ? • Ongoing research: toward fine mapping • additional markers and animals in the Lacaune purebred design • Additional data (L4) and markers in the Sarda*Lacaune BC design

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