Journal
JOURNAL OF ANIMAL SCIENCE
Volume 90, Issue 13, Pages 4690-4705Publisher
AMER SOC ANIMAL SCIENCE
DOI: 10.2527/jas.2012-5121
Keywords
Haemonchus contortus; linkage disequilibrium; quantitative trait loci; resistance; sheep
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Funding
- QTLMAP development team
- French Region Centre
- Toulouse Midi-Pyrenees bioinformatics platform
- Animal Genetics department of INRA
- ANR
- APISGENE (SheepSNPQTL project, Toulouse, France)
- EU (Osmoy, France) [FEOGA 024/m/1873]
- INRA grant (Department of Animal Health)
- INRA grant (Department of Animal Genetics)
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Gastrointestinal nematodes are one of the main health issues in sheep breeding. To identify loci affecting the resistance to Haemonchus contortus, a genome scan was carried out using 1,275 Romane x Martinik Black Belly backcross lambs. The entire population was challenged with Haemonchus contortus in 2 consecutive experimental infections, and fecal egg counts (FEC) and packed cell volumes were measured. A subgroup of 332 lambs with extreme FEC was necropsied to determine the total worm burden, length of female worms, sex ratio in the worm population, abomasal pH, and serum and mucosal G immunoglobulins (IgG) responses. Pepsinogen concentration was measured in another subset of 229 lambs. For QTL detection, 160 microsatellite markers were used as well as the Illumina OvineSNP50 BeadChip that provided 42,469 SNP markers after quality control. Linkage, association, and joint linkage and association analyses were performed with the QTLMAP software. Linkage disequilibrium (LD) was estimated within each pure breed, and association analyses were carried out either considering or not the breed origin of the haplotypes. Four QTL regions on sheep chromosomes (OAR) 5, 12, 13, and 21 were identified as key players among many other QTL with small to moderate effects. A QTL on OAR21 affecting pepsinogen concentration exactly matched the pepsinogen (PGA5) locus. A 10-Mbp region affecting FEC after the 1st and 2nd infections was found on OAR12. The SNP markers outperformed microsatellites in the linkage analysis. Taking advantage of the LD helped to refine the locations of the QTL mapped on OAR5 and 13.
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