Mapping quantitative trait loci controlling milk production in dairy cattle by exploiting progeny testing

Area of Science:

• Animal Genetics
• Quantitative Genetics
• Dairy Cattle Breeding

Background:

• Genetic variation in milk production is crucial for dairy cattle breeding.
• Identifying quantitative trait loci (QTL) aids in understanding and improving economically important traits.
• Progeny testing is a valuable method for estimating genetic merit in livestock.

Purpose of the Study:

• To map QTL influencing milk production traits in a selected dairy cattle population.
• To identify specific genomic regions associated with milk production variation.
• To assess the potential for marker-assisted selection in dairy cattle.

Main Methods:

• Utilized progeny testing with over 150,000 daughters' milk performances from 1,518 sires.
• Genotyped sires for 159 autosomal microsatellites across approximately two-thirds of the bovine genome.
• Employed maximum likelihood multilocus linkage analysis, accounting for phenotype variance heterogeneity.

Main Results:

• Identified five chromosomes (1, 6, 9, 10, and 20) with significant evidence (LOD score ≥ 3) for milk production QTL.
• Demonstrated that loci with substantial effects on milk production are still segregating in highly selected populations.
• Provided strong evidence for the genetic architecture of milk production in dairy cattle.

Conclusions:

• Significant QTL for milk production are present on chromosomes 1, 6, 9, 10, and 20.
• Highly selected dairy cattle populations harbor segregating loci with considerable effects on milk production.
• These findings support the implementation of marker-assisted selection for enhancing milk production traits.