Emphasis by dairy producers on milk, fat, and protein yields; somatic cell score (SCS); days open (DO) and dystocia score (DS) when culling was documented for U.S. Holstein cows that calved since 1980. Least-squares differences between cows retained for additional parities and those culled were estimated and converted to a standardized basis so that emphasis given to each trait for each parity could be expressed relative to milk yield for that parity. The most intense selection during first lactation was for milk and protein yields with less for fat (74 to 86% of that for milk), DO (18 to 74%), SCS (19 to 37%) and DS (7 to 15%). Producers emphasized the same traits when culling during second and third lactations. Trait emphasis by producers during culling could aid in determining trait emphasis when selecting bulls for progeny test and could also be useful for developing software for index-based culling guides.
Proceedings of the World Congress on Genetics Applied to Livestock Production, Volume , , 01.43, 2006
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