Originally published as Genetics Published Articles Ahead of Print on June 18, 2008.

Genetics, Vol. 179, 1539-1546, July 2008, Copyright © 2008
doi:10.1534/genetics.107.084483

Quantitative Trait Locus-by-Environment Interaction for Milk Yield Traits on Bos taurus Autosome 6

Marie Lillehammer*,1, Mike E. Goddard{dagger},{ddagger}, Heidi Nilsen*, Erling Sehested§, Hanne Gro Olsen*,**, Sigbjørn Lien*,{dagger}{dagger} and Theo H. E. Meuwissen*

* Department of Animal and Aquacultural Sciences, Norwegian University of Life Sciences, N-1432 Ås, Norway, {dagger} Department of Primary Industries, Attwood VIC 3049, Australia, {ddagger} University of Melbourne, Parkville 3010, Australia, § Geno Breeding and AI organization, N-1432 Ås, Norway, ** Bovibank, N-1431 Ås, Norway and {dagger}{dagger} Centre for Integrative Genetics (CIGENE), Norwegian University of Life Sciences, N-1432 Ås, Norway

1 Corresponding author: Department of Animal and Aquacultural Sciences, Norwegian University of Life Sciences, P.O. Box 5003, N-1432 Ås, Norway.
E-mail: marie.lillehammer{at}umb.no

Genotype-by-environment interactions for production traits in dairy cattle have often been observed, while QTL analyses have focused on detecting genes with general effects on production traits. In this study, a QTL search for genes with environmental interaction for the traits milk yield, protein yield, and fat yield were performed on Bos taurus autosome 6 (BTA6), also including information about the previously investigated candidate genes ABCG2 and OPN. The animals in the study were Norwegian Red. Eighteen grandsires and 716 sires were genotyped for 362 markers on BTA6. Every marker bracket was regarded as a putative QTL position. The effects of the candidate genes and the putative QTL were modeled as a regression on an environmental parameter (herd year), which is based on the predicted herd-year effect for the trait. Two QTL were found to have environmentally dependent effects on milk yield. These QTL were located 3.6 cM upstream and 9.1 cM downstream from ABCG2. No environmentally dependent QTL was found to significantly affect protein or fat yield.