We report putative quantitative trait loci affecting female fertility and milk production traits using the merged data from two research groups that conducted independent genome scans in Dairy Bull DNA Repository grandsire families to identify quantitative trait loci (QTL) affecting economically important traits. Six families used by both groups had been genotyped for 367 microsatellite markers covering 2713.5 cM of the cattle genome (90%), with an average spacing of 7.4 cM. Phenotypic traits included PTA for pregnancy rate and daughter deviations for milk, protein and fat yields, protein and fat percentages, somatic cell score, and productive life. Analysis of the merged dataset identified putative quantitative trait loci that were not detected in the separate studies, and the pregnancy rate PTA estimates that recently became available allowed detection of pregnancy rate QTL for the first time. Sixty-one putative significant marker effects were identified within families, and 13 were identified across families. Highly significant effects were found on chromosome 3 affecting fat percentage and protein yield, on chromosome 6 affecting protein and fat percentages, on chromosome 14 affecting fat percentage, on chromosome 18 affecting pregnancy rate, and on chromosome 20 affecting protein percentage. Within-family analysis detected putative QTL associated with pregnancy rate on six chromosomes, with the effect on chromosome 18 being the most significant statistically. These findings may help identify the most useful markers available for QTL detection and, eventually, for marker-assisted selection for improvement of these economically important traits.
Bibliographical noteFunding Information:
The authors thank members of regional project NC209 and the NRSP-8 cattle species coordinator for providing support for maintenance of the DBDR collection, and the contributing AI organizations for contributing semen to the Dairy Bull DNA Repository. We also thank Becky DeLuca, Larry Shade, Tina Sphon, and Melvin Tooker for technical assistance. This study was supported by the Agricultural Research Service , USDA project no. 1265-31000-073 and the United States-Israel Binational Agricultural Research and Development Fund (BARD) , project no. IS-238394C.
- Milk production traits
- Pregnancy rate
- Quantitative trait locus