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BMC Genomics. 2017 Aug 16;18(1):624. doi: 10.1186/s12864-017-3982-1.

The genomic architecture of mastitis resistance in dairy sheep.

Author information

1
The Roslin Institute and Royal (Dick) School of Veterinary Studies, University of Edinburgh, Easter Bush, Midlothian, EH25 9RG, UK.
2
Scotland's Rural College, Edinburgh, Easter Bush, Midlothian, EH25 9RG, UK.
3
School of Veterinary Medicine, Aristotle University of Thessaloniki, 54124, Thessaloniki, Greece.
4
School of Informatics, University of Bergen, 5008, Bergen, Norway.
5
The Roslin Institute and Royal (Dick) School of Veterinary Studies, University of Edinburgh, Easter Bush, Midlothian, EH25 9RG, UK. androniki.psifidi@roslin.ed.ac.uk.
6
Royal Veterinary College, University of London, AL9 7TA, Hatfield, UK. androniki.psifidi@roslin.ed.ac.uk.

Abstract

BACKGROUND:

Mastitis is the most prevalent disease in dairy sheep with major economic, hygienic and welfare implications. The disease persists in all dairy sheep production systems despite the implementation of improved management practises. Selective breeding for enhanced mastitis resistance may provide the means to further control the disease. In the present study, we investigated the genetic architecture of four mastitis traits in dairy sheep. Individual animal records for clinical mastitis occurrence and three mastitis indicator traits (milk somatic cell count, total viable bacterial count in milk and the California mastitis test) were collected monthly throughout lactation for 609 ewes of the Greek Chios breed. All animals were genotyped with a custom-made 960-single nucleotide polymorphism (SNP) DNA array based on markers located in quantitative trait loci (QTL) regions for mastitis resistance previously detected in three other distinct dairy sheep populations.

RESULTS:

Heritable variation and strong positive genetic correlations were estimated for clinical mastitis occurrence and the three mastitis indicator traits. SNP markers significantly associated with these mastitis traits were confirmed on chromosomes 2, 3, 5, 16 and 19. We identified pathways, molecular interaction networks and functional gene clusters for mastitis resistance. Candidate genes within the detected regions were identified based upon analysis of an ovine transcriptional atlas and transcriptome data derived from milk somatic cells. Relevant candidate genes implicated in innate immunity included SOCS2, CTLA4, C6, C7, C9, PTGER4, DAB2, CARD6, OSMR, PLXNC1, IDH1, ICOS, FYB, and LYFR.

CONCLUSIONS:

The results confirmed the presence of animal genetic variability in mastitis resistance and identified genomic regions associated with specific mastitis traits in the Chios sheep. The conserved genetic architecture of mastitis resistance between distinct dairy sheep breeds suggests that across-breed selection programmes would be feasible.

KEYWORDS:

California mastitis test; Chios sheep; Dairy sheep; Genomic association; Mastitis; Milk transcriptome; Sheep transcriptomic atlas; Somatic cell count; Total viable bacterial count; Transcription factor binding sites

PMID:
28814268
PMCID:
PMC5559839
DOI:
10.1186/s12864-017-3982-1
[Indexed for MEDLINE]
Free PMC Article

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