16S rRNA milk microbiota profiles on Holstein cows highlight QTL and provide a novel trait to assess the genetic regulation of mastitis H.J. Huson1, S.F. Lima2, R.C. Bicalho2 1Department of Animal Science, College of Agriculture and Life Sciences, Cornell University, Ithaca, NY, USA Hjh3@cornell.edu (Corresponding Author) 2Department of Population Medicine and Diagnostic Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY, USA It is well established that certain bacteria such as Escherichia coli, Steptrococcus uberis, and Staphylococcus aureus are causative agents of dairy cattle mastitis while other bacteria are associated with normal health and productivity. Pyrosequencing of the 16SrRNA gene from Holstein milk samples provided a means to generate individual cow milk microbiota profiles for which previous discriminant analysis of bacterial genera showed variation between healthy and clinical mastitis samples. This correlation was used to explore mastitis susceptibility in a genome-wide association study (GWAS) using 578,497 single-nucleotide polymorphisms (SNPs) spanning the bovine genome. The objective of this study was to explore the use of milk microbiota profiles for identifying novel QTL and subsequent candidate genes effecting mastitis. Comparative GWAS analyzed cows characterized as having clinical mastitis (CM) or healthy and compared results to a GWAS using a linear score based on their milk microbiota profile. Four genomic regions demonstrating association to CM incidence were identified on bos taurus autosomes (BTA) 5, 16, 26, and 29. Three regions on BTA 5, 26, and 29 were associated with the milk microbiota profiles. Previously published mastitis QTL were validated and novel QTL were identified on BTA 16 and 29. Over 15 potential genes were found in the associated regions of the 2 GWA studies. TBK1 on BTA 5 and RARRES3 and CTSE on BTA 29 appear the most promising candidate genes affecting immune response. Keywords: mastitis, genome-wide association, 16SrRNA, Holstein, microbiota

Heather J Huson, Svetlana F Lima, Rodrigo C Bicalho

Proceedings of the World Congress on Genetics Applied to Livestock Production, Volume Biology & Species - Bovine (dairy) 2, , 508, 2018
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