Originally published as Genetics Published Articles Ahead of Print on September 9, 2008.

Genetics, Vol. 180, 1211-1220, October 2008, Copyright © 2008
doi:10.1534/genetics.107.083964

Chromosomal Regions Underlying Noncoagulation of Milk in Finnish Ayrshire Cows

Anna-Maria Tyrisevä1, Kari Elo, Arja Kuusipuro, Veijo Vilva, Isto Jänönen, Heidi Karjalainen, Tiina Ikonen and Matti Ojala

Department of Animal Science, University of Helsinki, FI-00014 Helsinki, Finland

1 Corresponding author: Department of Animal Science, Koetilantie 5, P.O. Box 28, University of Helsinki, FI-00014 Helsinki, Finland.
E-mail: anna-maria.tyriseva{at}helsinki.fi

About 10% of Finnish Ayrshire cows produce noncoagulating milk, i.e., milk that does not form a curd in a standard 30-min testing time and is thus a poor raw material for cheese dairies. This phenomenon is associated with peak and midlactation, but some cows produce noncoagulating milk persistently. A genomewide scan under a selective DNA pooling method was carried out to locate genomic regions associated with the noncoagulation of milk. On the basis of the hypothesis of the same historical mutation, we pooled the data across sires. Before testing pools for homogeneity, allele intensities were corrected for PCR artifacts, i.e., shadow bands and differential amplification. Results indicating association were verified using daughter design and selective genotyping within families. Data consisted of 18 sire families with 477 genotyped daughters in total, i.e., 12% of each tail of the milk coagulation ability. Data were analyzed using interval mapping under maximum-likelihood and nonparametric methods. BMS1126 on chromosome 2 and BMS1355 on chromosome 18 were associated with noncoagulation of milk across families on an experimentwise 0.1% significance level. By scanning gene databases, we found two potential candidate genes: LOC538897, a nonspecific serine/threonine kinase on chromosome 2, and SIAT4B, a sialyltransferase catalyzing the last step of glycosylation of {kappa}-casein on chromosome 18. Further studies to determine the role of the candidates in the noncoagulation of milk are clearly needed.