Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 10, 2003
Publication Date: February 1, 2004
Citation: Van Tassell, C.P., Sonstegard, T.S., Ashwell, M.S. 2004. Mapping quantitative trait loci for dairy form in regions of chromosome 27 in two families of holstein. Journal of Dairy Science. 87(2):450-457.
Interpretive Summary: The objective of this study was to refine chromosomal regions containing effects on economically important traits. Specifically, effects associated with a conformation trait, dairy form, that is associated with the fatness of a cow. This trait has a negative genetic relationship with metabolic disorders and positive relationship with milk production. Results from this sstudy indicate that the regions identified may allow for selection to reduce metabolic disorders without impacting production traits. Detection of genetic markers located near important genes, like these, might be rewarding to breeders and also to researchers for use in marker-assisted selection. Selection on markers associated with these effects may increase genetic gain within these families and increase profits and sustainability for the US artificial insemination industry.
Preliminary marker association results for quantitative trait loci affecting conformation traits using the granddaughter design and eight large US Holstein grandsire families revealed strong associations in two families between the predicted transmitting abilities for dairy form and marker genotypes on bovine chromosome 27. Tests of marker associations for family 8 (85 sons) indicated an association with a microsatellite marker located near the telomere of chromosome 27. Interval analysis performed using additional marker genotypes generated for family 8 yielded evidence for a quantitative trait locus for dairy form near the telomere of chromosome 27. Only weak evidence was found for associations with milk production traits in this family. An association was also detected in family 2 (166 sons) with a microsatellite marker located approximately 21 cM from the centromere of chromosome 27. Interval analysis performed for family 2 yielded evidence for a quantitative trait locus for dairy form near BMS689 with no evidence of associations with production traits. Although phenotypic scores for dairy form are based on dairyness and body condition, this effect may be associated with fat metabolism. This hypothesis is supported by identification of similarly located quantitative trait loci in other cattle populations for marbling, milk fat yield, and milk fat percentage.