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item HEYEN, D
item Sonstegard, Tad
item Van Tassell, Curtis - Curt
item RON, M
item WELLER, J
item LEWIN, H

Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/15/2005
Publication Date: 11/1/2005
Citation: Ashwell, M.S., Heyen, D.W., Sonstegard, T.S., Van Tassell, C.P., Ron, M., Weller, J.I., Lewin, H.A. 2005. Detection of quantitative trait loci influencing conformation traits and calving ease in holstein-friesian cattle. Journal of Dairy Science. 88(11):4111-4119.

Interpretive Summary: Traditional methods of genetic selection have greatly improved milk production, but have difficulty improving some conformation traits and fitness traits like calving ease. Lack of selection for these economically important traits has a huge impact on global competitiveness, the sustainability of producers, and the entire dairy industry. The objective of this study was to identify DNA markers that can be used in the selection of bulls, with our long-term goal being to identify chromosomal regions that are important for milk production and female fertility in the US commercial Holstein population. The 29 cattle chromosomes were scanned with 404 DNA markers. Variations at some of these markers were associated with significant effects on most conformation traits and for calving ease. Application of DNA marker information for these traits should increase the rate of genetic improvement for milk production and fertility.

Technical Abstract: An extension of our previous genome scan of a North American Holstein-Friesian population was conducted in order to identify QTL affecting conformation traits. Resource families consisted of 1404 sons of 10 elite sires. Genome coverage was estimated to be 2713.5 cM (90%) for 406 markers using a granddaughter design. Regression interval mapping was used to detect QTL affecting 22 conformation traits, including body, udder, feet and legs, and dairy conformation as well as calving ease. Analysis of each family identified 74 genome-wise significant QTL influencing conformation traits on 21 chromosomes. Two genome-wise significant QTL influencing calving ease were detected on two chromosomes. Comparison of these results with other published reports identifies many common QTL affecting conformation traits. Chromosomal regions on BTA5, BTA6, BTA7, BTA15, BTA20, BTA22 and BTA26 appear to affect multiple traits, including conformation, milk production and somatic cell score, within the same family. The QTL identified in this study may be useful for MAS and the selection of positional candidate genes influencing these traits. Additional work is needed to determine the precise locations of the QTL before they can be used for MAS.