Mapping QTL Controlling Milk Somatic Cell Counts in Sheep and Goat Support the Polygenic Architecture the Mastitis Resistance

Abstract Text: QTLs for milk SCC were detected in two dairy sheep and goat designs including 1009 AI rams and 2254 Alpine and Sanen goats sired by 20 AI sires, respectively. Animals were genotyped with the 50K ovine and caprine SNP chips. Linkage and Linkage disequilibrium analyses were performed using the QTLmap software. The high number of chromosomal regions detected tended to confirm the polygenic architecture of the mastitis resistance trait. Many of these QTLs were population specific. Hence, it is difficult to tell extent to which the genetic architecture of resistance truly differs between species and breed. High significance combined to narrow confidence intervals of a few QTLs (OAR3 in sheep) and commonalties between breeds and species (OAR11 and CHI19) might help prioritizing chromosomal regions for further fine mapping and functional characterization.

Keywords: dairy sheep and goat, somatic cell count, QTL