Quantitative trait loci mapping of functional traits in the German Holstein cattle population

Quantitative Trait Loci Affecting Health Traits in Swedish Dairy Cattle

The purpose of this study was to map quantitative trait loci (QTL) affecting health traits in Swedish dairy cattle. A genome scan covering 17 chromosomes was performed. Ten grandsire families were used in a granddaughter design. Nine of the families belonged to the Swedish Red and White breed, which is related to other Nordic Ayrshire breeds, and one family was of the Swedish Holstein breed. A total of 417 bulls were genotyped for 116 microsatellite markers distributed over 17 chromosomes. Daughter yield deviations for clinical mastitis, somatic cell count (SCC), and other diseases (OD) were included in the analysis. Least squares interval mapping using putative QTL as cofactors was applied both within and across grandsire families. Significance thresholds were set by permutation tests. In the across-family analysis, we detected 8 suggestive QTL and 3 QTL significant at the genome level. The QTL affecting clinical mastitis were found on 3 chromosomes (9, 11, and 25), 4 QTL for SCC were found (on chromosomes 5, 9, 11, and 23), and we detected 4 QTL for OD (on chromosomes 9, 11, 15, and 25). In addition, we found several QTL that segregated within single families but where the QTL effect was not significant in the across-family analysis. In conclusion, we were able to locate QTL for all 3 analyzed traits, and overlapping QTL for several traits were observed.

Quantitative Trait Loci for Health Traits in Finnish Ayrshire Cattle

A whole-genome scan was conducted to search for quantitative trait loci (QTL) affecting health traits in Finnish Ayrshire dairy cattle. The mapping population consisted of 12 bulls and their 491 sons in a granddaughter design. A total of 150 markers were typed covering all 29 autosomes. The traits under study were somatic cell score, mastitis, and a group of other veterinary treatments. Effects of the QTL and positions were estimated with the regression method. When carrying out interval mapping on each chromosome, cofactors were used to adjust for QTL identified at other chromosomes. Empirical P-values were obtained by permutation. Altogether 17 QTL were detected with genomewise significant P-values in the across family analysis. Quantitative trait loci affecting SCS were identified on chromosomes 1, 3, 11, 18, 21, 24, 27, 29, and QTL for mastitis on chromosomes 14, 18. Quantitative trait loci for other veterinary treatments were found on chromosomes 1, 2, 5, 8, 15, 22, and 23. The allele substitution effects were from 0.5 to 1.7 genetic standard deviations. The positions of these health QTL did not overlap with milk QTL detected in previous studies of the same population.

The telomeric region of BTA18 containing a potential QTL region for health in cattle exhibits high similarity to the HSA19q region in humans

We have applied a targeted physical mapping approach, based on the isolation of bovine region-specific large-insert clones using homologous human sequences and chromosome microdissection, to enhance the physical gene map of the telomeric region of BTA18 and to prove its evolutionary conservation. The latter is a prerequisite to exploit the dense human gene map for future positional cloning approaches. Partial sequencing and homology search were used to characterize 20 BACs targeted to the BTA18q2.4-q2.6 region. We used fluorescence in situ hybridization (FISH) to create physical maps of 11 BACs containing 15 gene loci; these BACs served as anchor loci. Using these approaches, 12 new gene loci (CKM, STK13, PSCD2, IRF3, VASP, ACTN4, ITPKC, CYP2B6, FOSB, DMPK, MIA, SIX5) were assigned on BTA18 in the bovine cytogenetic map. A resolved physical map of BTA18q2.4-q2.6 was developed, which encompasses 28 marker loci and a comparative cytogenetic map that contains 15 genes. The mapping results demonstrate the high evolutionary conservation between the telomeric region of BTA18q and HSA19q.