Atypical progesterone profiles have been associated with compromised fertility and reduced conception rate (Darwash et al. 1998), and also an antagonistic correlation with milk yield in early lactation (Nyman et al., 2014). Our study aimed to identify genomic regions and causal variants associated with normal and atypical progesterone profiles in Holstein-Friesian dairy cows. Firstly, genome-wide association studies (GWAS) were executed using Illumina BovineSNP50 v1 BeadChip (50K) genotypes to identify the most promising genomic regions for the traits and secondly, the associated regions were fine-mapped by using imputed sequences. In a 8820 basepair region on chromosome 17, SNPs significantly associated with Delayed cyclicity and Commencement of Luteal Activity (CLA) (-Log10(P-value)=4.64 and 4.07 respectively) were identified. These two traits are physiologically very similar and have similar heritabilities which are why these finding could be expected. The regions found in this study can be used for further analysis to identify regulatory genes and variants that may explain variation in Delayed cyclicity and CLA. Keywords: dairy cattle, progesterone profiles, GWAS, imputation, whole genome sequences

Sofia Nyman, Sandrine Duchemin, DJ de Koning, Britt Berglund

Proceedings of the World Congress on Genetics Applied to Livestock Production, Volume Biology - Reproduction 1, , 380, 2018
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