A search for quantitative trait loci for milk production traits on chromosome 6 in Finnish Ayrshire cattle

Anim Genet. 1999 Apr;30(2):136-43. doi: 10.1046/j.1365-2052.1999.00435.x.


Cattle chromosome 6 was scanned with 11 markers, ten microsatellites and the casein haplotype, to identify quantitative trait loci (QTLs) affecting the following milk production traits: milk yield, fat percentage, fat yield, protein percentage and protein yield. Twelve Finnish Ayrshire half-sib families with a total of 480 sons were genotyped and used in a grand-daughter design. Interval mapping was performed with a multiple-marker regression approach with a one-QTL and a two-QTL model, and the significance threshold values were determined empirically using a permutation test. Across-family analysis with the one-QTL model revealed an effect on protein percentage (P < 0.05) and on milk yield (P < 0.05). The analysis with the two-QTL model identified significant effects (P < 0.05) on protein percentage, milk yield, and fat yield. Comparing these two cases, the results suggest the existence of two QTLs on chromosome 6 with an effect on milk production traits. One of the QTLs was located around the casein genes. As the other QTL was similar in location and effect to a QTL found previously in Holstein-Friesians, an identity-by-descent approach could be applied to fine map this region.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Caseins / genetics
  • Cattle / genetics*
  • Cattle / physiology
  • Chromosome Mapping / veterinary
  • Computer Simulation
  • DNA Primers / chemistry
  • Electrophoresis, Polyacrylamide Gel / veterinary
  • Female
  • Finland
  • Inbreeding
  • Lactation / genetics*
  • Lipids / biosynthesis
  • Lipids / genetics
  • Male
  • Microsatellite Repeats / genetics
  • Milk / metabolism*
  • Milk Proteins / biosynthesis
  • Milk Proteins / genetics
  • Models, Genetic
  • Polymerase Chain Reaction / veterinary
  • Quantitative Trait, Heritable*
  • Regression Analysis
  • Semen / chemistry


  • Caseins
  • DNA Primers
  • Lipids
  • Milk Proteins