Chromosomal Regions Underlying Noncoagulation of Milk in Finnish Ayrshire Cows

Abstract

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 k-casein on chromosome 18. Further studies to determine the role of the candidates in the noncoagulation of milk are clearly needed.

Mapping and fine-mapping of genetic factors affecting bovine milk composition

“…These milk protein fractions, mainly representing caseins, are encoded on BTA6 and thus, the recombination among alleles is small (Bittante et al, 2012). In contrast, Tyrisevä et al (2008) did not find significant associations between NC milk and the casein loci. In the present study, the casein loci were included as part of the design of our GWAS with NC milk, resulting in significant associations that are independent from the casein loci.…”

“…Their QTL is very close to the 7 MBP region identified in our study. The methodology used by Tyrisevä et al (2008) is different from the present study. It is important to note that the study by Tyrisevä et al (2008) is based on a linkage study within sire families with pooled DNA of cows with extreme phenotypes, and our study is based on an association analysis of genotyped cows with scored phenotypes.…”

“…The methodology used by Tyrisevä et al (2008) is different from the present study. It is important to note that the study by Tyrisevä et al (2008) is based on a linkage study within sire families with pooled DNA of cows with extreme phenotypes, and our study is based on an association analysis of genotyped cows with scored phenotypes. Both methodologies have the common goal of pointing out the potential candidate genes associated with a trait of interest, and, despite the differences between both studies, a similar genomic region was associated with NC milk.…”

“…Studies by Jensen et al (2012) and by Gregersen et al (2015) suggest that poor-and non-coagulation of milk are influenced by the milk protein variants of the k-casein gene. In contrast, study by Tyrisevä et al (2008) and Gregersen et al (2015) revealed that non-coagulation of milk can be influenced by other parts of the cattle genome too.…”

“…These 7 MBP explain large fractions of the phenotypic variation in NC milk, ranging from 7% to 11%. Tyrisevä et al (2008) performed a genome scan to map non-coagulation of milk in 477 genotyped FAY cows. Their study used microsatellite markers and identified a QTL located around 17 MBP on BTA18.…”