Genetic evaluation for yield traits in dairy cattle is in Denmark currently based on an Animal Model (AM) for 305-d lactation records. Implementation of a random regression (RR) test day (TD) model is in preparation. The existing lactation model uses lactation records from 1984 and onwards; TD records are only available from 1990 and onwards. In order to utilize data from the same time span in a TD model as in the present lactation model, a blending procedure including both TD and lactation records is needed. Furthermore, a planned joint genetic evaluation of dairy cattle in the Nordic countries must be based on a model that is able to handle both lactation and TD records. This is because Finland and soon Denmark will use a TD model, while Sweden and Norway will continue using a lactation model for genetic evaluation. The main objective for this study was to develop a model using both TD records and lactation records. To test the approach, first lactation protein yields for Holsteins in a region of Denmark were used. A multitrait model for TD records and 305-d records was developed. Different scenarios illustrating the situations where blending will be needed were investigated and correlations between predicted breeding values (BV) in different scenarios were computed
Proceedings of the World Congress on Genetics Applied to Livestock Production, Volume 2002. Session 1, , 1.02, 2002
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