Using single-step genetic evaluation for type traits in the Nordic countries

In the Nordic Cattle Genetic Evaluation NAV (Denmark, Finland and Sweden) we are studying the use of the single-step approach to estimate genomic breeding values for Nordic Holstein cattle. The method used is a single-step GTBLUP model with blending of foreign information, and the traits in this report are the two type traits: chest width and udder depth. Breeding values estimated from single-step models using a full and a reduced dataset are compared and validated by Interbull validation and the Legarra Reverter Regression method. The mean GEBV’s by birth year shows similar level for single-step full and single-step reduced and the correlation between those GEBV’s are high. The validation results are as expected, and the results do not show any indication of GEBV inflation. The single-step model included a polygenic effect and two levels of polygenic effects (10% and 30%) were analyzed using a regression model for domestic AI bulls that were divided into groups based on number of daughters. It was found that polygenic effect of 30% were fitting best for the type traits with single-step approach for Nordic cattle.