Microbiome analysis of the skin of sheep that are resistant or susceptible to breech flystrike

Context: Breech strike is a serious disease for wool sheep. Skin wrinkle and dags are known predisposing factors for breech strike; however, a large part of the variation among sheep is unknown. Aims: We studied the natural diversity and difference in microbial populations in the skin around the breech area in Merino sheep genetically resistant and susceptible to breech strike, by using 16S rRNA gene sequence analysis. Methods: The sheep were from the breech strike flocks at the Mount Barker research station in Western Australia and from the CSIRO research station near Armidale in New South Wales. Skin samples were collected from the breech of all 2013-born progeny in both flocks before they were struck. Yearling ewes and rams were then naturally exposed to challenge by Lucilia cuprina blowflies. Breeding values for breech strike were estimated and used with phenotypic data to identify breech strike-resistant and -susceptible sheep. Skin samples of 78 unstruck and 73 struck sheep were selected, their microbiomes were analysed using 16S rRNA meta-barcoding, and operational taxonomic unit counts were analysed. Results: The diversity analyses showed that the two flocks in the different environments had different microbiome profiles, but no difference was found between sexes or between breech strike-resistant and -susceptible sheep in either flock. Conclusions: The results indicated that microbial differences on the skin of sheep are not associated with differences in susceptibility to breech strike. Implications: Microbial differences do not offer opportunities to manage breech strike in Merino sheep.