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item Ashwell, Melissa
item Van Tassell, Curtis - Curt
item Sonstegard, Tad

Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/12/2001
Publication Date: 11/1/2001
Citation: Ashwell, M.S., Van Tassell, C.P., Sonstegard, T.S. 2001. A genome scan to identify quantitative trait loci affecting economically important traits in a us holstein population. Journal of Dairy Science. 84(11):2535-2542.

Interpretive Summary: The objective of this study was to identify DNA markers that could be used in the selection of bulls, with our long-term goal being to identify chromosomal regions important for milk production, health, and type traits in the US commercial Holstein population. Detection of genetic markers located near important genes controlling these traits might be rewarding to breeders and also to researchers for use in marker-assisted selection. A total of 155 DNA markers located on 29 chromosomes were studied in eight large US Holstein families. Variations with some of these DNA markers were associated with significant effects for milk production, conformation traits, and somatic cell score in several families. Selection on these markers may increase genetic gain within these families and increase profits and sustainability for the US artificial insemination industry.

Technical Abstract: Quantitative trait loci (QTL) affecting economically important traits were studied for eight large Holstein grandsire families using the granddaughter design. A total of 155 microsatellite markers were selected for the scan. The data analyzed include genotypes for 50 markers not previously reported. Results' analyses of 105 marker genotypes reported previously were updated. .Effects of marker alleles were analyzed for 38 traits including traits for milk production, somatic cell score, productive life, conformation, calving ease, and 16 canonical traits derived from conformation and production traits. Permutation tests were used to calculate empirical trait-wise error rates. A trait-wise critical value of P = 0.1 was used to determine significance. Ten putative QTL associated with 7 of the new markers were identified within specific families. One marker on chromosome (chr.) 14 was associated with differences in fat yield, fat percentage and a canonical production trait in two families. Markers on chromosomes 18 and 22 were associated with differences in rump angle in the same family. Markers were associated with differences in udder depth and fore udder attachment on chromosomes 16 and 20, respectively. One marker on chr. 27 was associated with a difference in the dairy capacity composite index and another marker on chr. 13 was associated with a difference in a canonical conformation trait. These additional markers complete our genome-scan to identify QTL affecting economically important traits in a selected commercial Holstein population. The QTL identified in this genome scan may be useful for marker-assisted selection to increase the rate of genetic improvement on traits such as disease resistance and conformation traits associated with fitness while accelerating genetic improvement for production.