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Title: TRAIT SELECTION WHEN CULLING U.S. HOLSTEINS

Author
item Norman, H
item Hutchison, Jana
item Wright, Janice
item Kuhn, Melvin

Submitted to: World Congress of Genetics Applied in Livestock Production
Publication Type: Proceedings
Publication Acceptance Date: 5/6/2006
Publication Date: 8/13/2006
Citation: Norman, H.D., Hutchison, J.L., Wright, J.R., Kuhn, M.T. 2006. Trait selection when culling U.S. Holsteins. 8th World Congress of Genetics Applied in Livestock Production. Communication 01-43.

Interpretive Summary: 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.

Technical Abstract: 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.