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

T. M Villumsen, P. Madsen, J. Jensen, J. H Jakobsen

Proceedings of the World Congress on Genetics Applied to Livestock Production, Volume 2002. Session 1, , 1.02, 2002
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