Characterization of a QTL region affecting clinical mastitis and protein yield on BTA6

Abstract

Quantitative trait loci affecting clinical mastitis were detected and fine mapped to a narrow region on bovine chromosome 6 in the Norwegian Red cattle population. The region includes the casein gene cluster and several candidate genes thought to influence clinical mastitis. The most significant results were found for SNPs within the Mucin 7 gene. This gene encodes an antimicrobial peptide and constitutes part of the first line of defence for the mucosal immune system. Detection of long haplotypes extending several Mb may indicate that artificial selection has influenced the haplotype structures in the region. A search for selection sweeps supports this observation and coincides with association results found both by single SNP and haplotype analyses. Our analyses identified haplotypes carrying quantitative trait loci alleles associated with high protein yield and simultaneously fewer incidences of clinical mastitis. The fact that such haplotypes are found in relative high frequencies in Norwegian Red may reflect the combined breeding goal that is characterized by selection for both milk production and disease resistance. The identification of these haplotypes raises the possibility of overcoming the unfavourable genetic correlation between these traits through haplotype-assisted selection.

Genome-wide association study using high-density single nucleotide polymorphism arrays and whole-genome sequences for clinical mastitis traits in dairy cattle

“…Several studies have reported associations with SCC/CM with genomic region on BTA6 similar to those in the present study; for example, in US Holstein (Cole et al 2011), German Holstein (Abdel-Shafy et al, 2014, and Norwegian Red cattle (Nilsen et al, 2009;Sodeland et al, 2011). Meredith et al (2013) identified associations on BTA 13 and BTA 20, similar to the current study.…”

A genome-wide association study for somatic cell score using the Illumina high-density bovine beadchip identifies several novel QTL potentially related to mastitis susceptibility

“…The size of the QTL, however, made it impossible to pinpoint particular candidate genes that might be associated with the trait. An association with CM near the casein gene complex at ~90 Mb on chromosome 6 has also been identified (Nilsen et al, 2009; Sodeland et al, 2011). This region was not significantly associated with SCS in our study, however.…”

Single nucleotide polymorphisms in the CXCR1 gene and its association with clinical mastitis incidence in Polish Holstein-Friesian cows

“…Since it is observed that some cows are more resistant to mastitis, it is believed that the susceptibility to this disease could be genetically affected. Consequently, the search for genetic markers possibly associated with udder health is being carried out (Nilsen et al, 2009;Ogorevc et al, 2009). The identification of such markers could lead to the selection of mastitis-resistant cows, which would result in improved herd health and increased efficiency of milk production.…”