Submitted to: Animal Genetics International Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: June 1, 2000
Publication Date: July 22, 2000
Citation: Ashwell, M.S., Heyen, D.W., Da, Y., Sonstegard, T.S., Van Tassell, C.P., Lewin, H.A. 2000. Detection of qtl affecting milk production in 6 dairy bull dna repository grandsire families.. Animal Genetics International Conference Proceedings.
Originally two research groups conducted independent genome scans in Dairy Bull DNA Repository grandsire families to identify quantitative trait loci (QTL) affecting economically important traits. Each group selected eight families for study, six that were common across both studies. We report putative QTL affecting milk production traits using the merged data from the two groups. The six common families were genotyped at 367 microsatellite markers. Genome coverage was estimated to be 2713.5cM (90%), with an average spacing of 7.4cM. QTL Express software (http://qtl.cap.ed.ac.uk) was used for regression interval mapping within each family. Phenotypic traits included daughter deviations for milk, protein and fat yields, protein and fat percentages, somatic cell score and productive life, weighted by their respective reliabilities. Permutation was used to calculate chromosome-wide P < 0.05 and P < 0.01 significance thresholds. One hundred seven putative marker effects were identified at P < 0.05, 36 of these at P < 0.01. Highly significant effects (P << 0.01, F-statistic > 15) were found on chromosome (BTA) 3 affecting fat percentage and protein yield, BTA6 affecting protein percentage, and BTA14 affecting fat percentage and yield. Interval analysis of the merged dataset identified putative QTL not detected in the separate studies. QTL identified in this study may be useful for marker-assisted selection to improve milk production and manipulate milk protein and fat components.