Authors
M. S. Khatkar, P. C. Thomson, I. Tammen, F. Costa and H. W. Raadsma

Background
Many studies have been conducted to detect quantitative trait loci (QTL) in dairy cattle. However, these studies are diverse in terms of their differing resource populations, marker maps, phenotypes, etc, and one of the challenges is to be able to synthesise this diverse information. This web page has been constructed to provide an accessible database of studies, providing a summary of each study, facilitating an easier comparison across studies. However, it also highlights the need for uniform reporting of results of studies, to facilitate more direct comparisons being made.

Description
Studies recorded in this database include complete and partial genome scans, single chromosome scans, as well as fine mapping studies, and contain all known reports that were published in peer-reviewed journals and readily available conference proceedings, initially up to April 2005. However, this data base is being added to, as indicated by the last web update. Note that some duplication of results will occur, in that there may be a number of reports on the same resource population, but utilising different marker densities or different statistical methodologies. The traits recorded in this map are milk yield, milk composition (protein yield, protein %, fat yield, fat %), and somatic cell score (SCS).

QTL Map Online
Clicking on a dot displays a popup table of detailed information about that QTL, namely resource population and design, analytical method, marker map used, map position with confidence interval, closest marker, test statistic, effect size and reference. Note that some of the entries in this online map are incomplete, due to a lack of reported information in the cited reference. The dots on the map show the reported QTL over the entire cattle genome at 30 cM intervals.

Each dot represents a different QTL report with the colour intensity indicating the level of significance for the QTL:

P < 0.001 or reported as highly significant;

0.001 < P < 0.01 or reported as significant;

0.01 < P < 0.05 or reported as marginally significant;

Meta QTL.

More Information
A review and meta-analysis of these data can be found in Khatkar et al. (2004).

Feedback
To help make this a valuable resource to the dairy cattle genetics community, please send us:

• any omissions or recent publications not included;
• suggestions for improvement of this web site; or
• any other queries about the project

Reference
Khatkar, MS, Thomson, PC, Tammen, I and Raadsma HW. 2004.Quantitative trait loci mapping in dairy cattle: review and meta-analysis Genet. Sel. Evol. 36:163-190.