Phenotypic, genetic and genome-wide associations for ketosis and metabolic disease indicators on the basis of cow reference groups
Metabolic disorders display a major part of early lactation disease complexes including ketosis as one of the most common metabolic disorder and an access condition for other diseases in high-yielding dairy cattle i.e., Holstein cows. High economic losses for dairy farmers due to ketosis highlighted the importance of incorporating management and ... breeding strategies to monitor and prevent ketosis. Today, routine milk sampling using Fourier-transform infrared spectroscopy (FTIR) allows the determination of novel innovative traits of practical interest for dairy farmers in metabolic disease prevention. In particular, new health traits limited historical data and genomic selection regarding those traits is challenging. A smaller reference population is available to be used in genomic predictions compared with e.g., milk production traits. Genotyping of cows in herds with reliable health records may be one strategy to enhance the accuracy of genomic predictions for health and novel indicator traits. Thus, cow reference groups offer new prospects in dairy cattle breeding for improved disease resistance by combining phenotypes for novel traits with high-density genetic markers. Against this background, we assessed the usability of common and novel milk measurements i.e., the relation between novel functional FTIR measurements, fertility trait interval from calving to first insemination and ketosis diagnosis on the basis of cow reference groups on different scales: 1) Examination of relations between milk indicator traits and ketosis, phenotypically; 2) Estimation of (co)variance components for such traits considering different relationship matrices on quantitative genetic scales; 3) Genome-wide association studies (GWAS), identification of associated single nucleotide polymorphisms (SNP) and candidate genes for the ketosis diagnosis, innovative milk indicator traits and the fertility interval trait in Holstein cattle.