Quantitative trait loci affecting milk yield and composition, health, and type traits were studied for seven large grandsire families of US Holstein using the granddaughter design. The families were genotyped at 20 microsatellite markers on 15 chromosomes, and the effects of the marker alleles were analyzed for 28 traits (21 type traits, 5 milk yield and composition traits, somatic cell score, and productive herd life). Markers BM415 on chromosome 6 and BM6425 on chromosome 14 were associated with effects on protein percentage in a single grandsire family. The latter marker had a lower probability of being associated with changes in milk yield and fat percentage in the same family. Increases in productive herd life were associated with an allele at marker BM719 on chromosome 16 in one grandsire family.
Bibliographical noteFunding Information:
The authors thank Tom Lawlor (Holstein Association USA, Brattleboro, VT) for providing the type trait data. We thank the members of Regional Project NC209, especially Harris Lewin, and the contributing AI organizations for initiating, maintaining, and contributing to the Dairy Bull DNA Repository. We also thank Larry Shade for technical assistance. This work was supported by the Agricultural Research Service, USDA Project 1265-31000-039-00D.
- Microsatellite markers
- Milk yield traits
- Quantitative trait loci
- Type traits