Study of Relationships Between Production and Fertility Traits in Dairy Cattle Using Molecular Data

Selection strategies focusing on milk yield in dairy cattle have generally led to a decline in fertility (Pryce et al. 2004). This fact is due to an antagonistic relationship between production and reproduction, which has been proven via the estimation of genetic correlations in quantitative genetic studies (e.g. König et al. 2009). Novel molecular techniques can be used to get a deeper insight into fertility mechanisms and a detailed explanation of relationships between fertility and production on the gene level. In our studies of gene expression changes in bovine endometrium during the estrous cycle (Bauersachs et al. 2005; Mitko et al. 2008) we have found a number of genes up-regulated in the luteal phase compared to the ovulatory phase. This up-regulation suggests a potential role of these genes for proper development of the early embryo and for successful pregnancy establishment and maintenance since the steroid hormone progesterone (P4) plays a key role in these reproductive events in the endometrium (reviewed in Bauersachs et al. 2008). Importantly, these candidate genes have been recovered in the target species and gender. The objective of this work was to integrate these findings from functional genomics into association analyses for fertility and production traits in dairy cattle. Hence, this work can make an additional contribution to the evidence of antagonistic relationships between production and reproduction based on a novel concept. Detection of (unexpected) beneficial SNP-genotypes for both production and reproduction within candidate genes would provide the potential to improve production without decreasing fertility.