Bovine chromosomal regions affecting rheological traits in acid-induced skim milk gels.

The production of fermented milk products has increased worldwide during the last decade and is expected to continue to increase during the coming decade. The quality of these products may be optimized through breeding practices; however, the relations between cow genetics and technological properties of acid milk gels are not fully known. Therefore, the aim of this study was to identify chromosomal regions affecting acid-induced coagulation properties and possible candidate genes. Skim milk samples from 377 Swedish Red cows were rheologically analyzed for acid-induced coagulation properties using low-amplitude oscillation measurements. The resulting traits, including gel strength, coagulation time, and yield stress, were used to conduct a genome-wide association study. Single nucleotide polymorphisms (SNP) were identified using the BovineHD SNPChip (Illumina Inc., San Diego, CA), resulting in almost 621,000 segregating markers. The genome was scanned for putative quantitative trait loci (QTL) regions, haplotypes based on highly associated SNP were inferred, and the additive genetic effects of haplotypes within each QTL region were analyzed using mixed models. A total of 8 genomic regions were identified, with large effects of the significant haplotype explaining between 4.8 and 9.8% of the phenotypic variance of the studied traits. One major QTL was identified to overlap between gel strength and yield stress, the QTL identified with the most significant SNP closest to the gene coding for κ-casein (CSN3). In addition, a chromosome-wide significant region affecting yield stress on BTA 11 was identified to be colocated with PAEP, coding for ß-lactoglobulin. Furthermore, the coagulation properties of the genetic variants within the 2 genes were compared with the coagulation properties identified by the patterns of the haplotypes within the regions, and it was discovered that the haplotypes were more diverse and in one case slightly better at explaining the phenotypic variance. Besides these significant QTL comprising the 2 milk proteins, 3 additional genes are proposed as possible candidates, namely RAB22A, CDH13, and STAT1, and all have previously been found to be expressed in the mammary gland. To our knowledge, this is the first attempt to map QTL regions for acid-induced coagulation properties.

Bovine chromosomal regions affecting rheological traits in rennet-induced skim milk gels.

Optimizing cheese yield and quality is of central importance to cheese manufacturing. The yield is associated with the time it takes before the gel has an optimal consistency for further processing, and it is well known that gel formation differs between individual milk samples. By identifying genomic regions affecting traits related to rennet-induced gelation, the aim of this study was to identify potential candidate genes affecting these traits. Hence, rennet-induced gelation, including rennet coagulation time, gel strength, and yield stress, was measured in skim milk samples collected from 379 animals of the Swedish Red breed using low-amplitude oscillation measurements. All animals had genotypes for almost 621,000 segregating single nucleotide polymorphisms (SNP), identified using the Bovine HD SNPChip (Illumina Inc., San Diego, CA). The genome was scanned for associations, haplotypes based on SNP sets comprising highly associated SNP were inferred, and the effects of the 2 most common haplotypes within each region were analyzed using mixed models. Even though the number of animals was relatively small, a total of 21 regions were identified, with 4 regions showing association with more than one trait. A major quantitative trait locus for all traits was identified around the casein cluster explaining between 9.3 to 15.2% of the phenotypic variation of the different traits. In addition, 3 other possible candidate genes were identified; that is, UDP-N-acetyl-α-d-galactosamine:polypeptide N-acetylgalactosaminyl-transferase 1 (GALNT1), playing a role in O-glycosylation of κ-casein, and 2 cathepsins, CTSZ and CTSC, possibly involved in proteolysis of milk proteins. We have shown that other genes than the casein genes themselves may be involved in the regulation of gelation traits. However, additional analysis is needed to confirm these results. To our knowledge, this is the first study identifying quantitative trait loci affecting rennet-induced gelation of skim milk through a high-density genome-wide association study.

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

Mastitis is a mammary disease that frequently affects dairy cattle. Despite considerable research on the development of effective prevention and treatment strategies, mastitis continues to be a significant issue in bovine veterinary medicine. To identify major genes that affect mastitis in dairy cattle, 6 chromosomal regions on Bos taurus autosome (BTA) 6, 13, 16, 19, and 20 were selected from a genome scan for 9 mastitis phenotypes using imputed high-density single nucleotide polymorphism arrays. Association analyses using sequence-level variants for the 6 targeted regions were carried out to map causal variants using whole-genome sequence data from 3 breeds. The quantitative trait loci (QTL) discovery population comprised 4,992 progeny-tested Holstein bulls, and QTL were confirmed in 4,442 Nordic Red and 1,126 Jersey cattle. The targeted regions were imputed to the sequence level. The highest association signal for clinical mastitis was observed on BTA 6 at 88.97 Mb in Holstein cattle and was confirmed in Nordic Red cattle. The peak association region on BTA 6 contained 2 genes: vitamin D-binding protein precursor (GC) and neuropeptide FF receptor 2 (NPFFR2), which, based on known biological functions, are good candidates for affecting mastitis. However, strong linkage disequilibrium in this region prevented conclusive determination of the causal gene. A different QTL on BTA 6 located at 88.32 Mb in Holstein cattle affected mastitis. In addition, QTL on BTA 13 and 19 were confirmed to segregate in Nordic Red cattle and QTL on BTA 16 and 20 were confirmed in Jersey cattle. Although several candidate genes were identified in these targeted regions, it was not possible to identify a gene or polymorphism as the causal factor for any of these regions.

Effects of breed and casein genetic variants on protein profile in milk from Swedish Red, Danish Holstein, and Danish Jersey cows.

In selecting cows for higher milk yields and milk quality, it is important to understand how these traits are affected by the bovine genome. The major milk proteins exhibit genetic polymorphism and these genetic variants can serve as markers for milk composition, milk production traits, and technological properties of milk. The aim of this study was to investigate the relationships between casein (CN) genetic variants and detailed protein composition in Swedish and Danish dairy milk. Milk and DNA samples were collected from approximately 400 individual cows each of 3 Scandinavian dairy breeds: Swedish Red (SR), Danish Holstein (DH), and Danish Jersey (DJ). The protein profile with relative concentrations of α-lactalbumin, ß-lactoglobulin, and α(S1)-, α(S2)-, κ-, and ß-CN was determined for each milk sample using capillary zone electrophoresis. The genetic variants of the α(S1)- (CSN1S1), ß- (CSN2), and κ-CN (CSN3) genes for each cow were determined using TaqMan SNP genotyping assays (Applied Biosystems, Foster City, CA). Univariate statistical models were used to evaluate the effects of composite genetic variants, α(S1)-ß-κ-CN, on the protein profile. The 3 studied Scandinavian breeds differed from each other regarding CN genotypes, with DH and SR having similar genotype frequencies, whereas the genotype frequencies in DJ differed from the other 2 breeds. The similarities in genotype frequencies of SR and DH and differences compared with DJ were also seen in milk production traits, gross milk composition, and protein profile. Frequencies of the most common composite α(S1)-ß-κ-CN genotype BB/A(2)A(2)/AA were 30% in DH and 15% in SR, and cows that had this genotype gave milk with lower relative concentrations of κ- and ß-CN and higher relative concentrations of αS-CN, than the majority of the other composite genotypes in SR and DH. The effect of composite genotypes on relative concentrations of the milk proteins was not as pronounced in DJ. The present work suggests that a higher frequency of BB/A(1)A(2)/AB, together with a decrease in BB/A(2)A(2)/AA, could have positive effects on DH and SR milk regarding, for example, the processing of cheese.

The occurrence of noncoagulating milk and the association of bovine milk coagulation properties with genetic variants of the caseins in 3 Scandinavian dairy breeds.

Substantial variation in milk coagulation properties has been observed among dairy cows. Consequently, raw milk from individual cows and breeds exhibits distinct coagulation capacities that potentially affect the technological properties and milk processing into cheese. This variation is largely influenced by protein composition, which is in turn affected by underlying genetic polymorphisms in the major milk proteins. In this study, we conducted a large screening on 3 major Scandinavian breeds to resolve the variation in milk coagulation traits and the frequency of milk with impaired coagulation properties (noncoagulation). In total, individual coagulation properties were measured on morning milk collected from 1,299 Danish Holstein (DH), Danish Jersey (DJ), and Swedish Red (SR) cows. The 3 breeds demonstrated notable interbreed differences in coagulation properties, with DJ cows exhibiting superior coagulation compared with the other 2 breeds. In addition, milk samples from 2% of DH and 16% of SR cows were classified as noncoagulating. Furthermore, the cows were genotyped for major genetic variants in the αS1- (CSN1S1), ß- (CSN2), and κ-casein (CSN3) genes, revealing distinct differences in variant frequencies among breeds. Allele I of CSN2, which had not formerly been screened in such a high number of cows in these Scandinavian breeds, showed a frequency around 7% in DH and DJ, but was not detected in SR. Genetic polymorphisms were significantly associated with curd firming rate and rennet coagulation time. Thus, CSN1S1 C, CSN2 B, and CSN3 B positively affected milk coagulation, whereas CSN2 A(2), in particular, had a negative effect. In addition to the influence of individual casein genes, the effects of CSN1S1-CSN2-CSN3 composite genotypes were also examined, and revealed strong associations in all breeds, which more or less reflected the single gene results. Overall, milk coagulation is under the influence of additive genetic variation. Optimal milk for future cheese production can be ensured by monitoring the frequency of unfavorable variants and thus preventing an increase in the number of cows producing milk with impaired coagulation. Selective breeding for variants associated with superior milk coagulation can potentially increase raw milk quality and cheese yield in all 3 Scandinavian breeds.

A molecular study of congenital erythropoietic porphyria in cattle.

Previous studies have shown that congenital erythropoietic porphyria (CEP) in cattle is caused by an inherited deficiency of the enzyme uroporphyrinogen III synthase (UROS) encoded by the UROS gene. In this study, we have established the pedigree of an extended Holstein family in which the disease is segregating in a manner consistent with autosomal recessive inheritance. Biochemical analyses demonstrated accumulation of uroporphyrin, thus confirming that it is indeed insufficient activity of UROS which is the cause of the disease. We have therefore sequenced all nine exons of UROS in affected and non-affected individuals without detecting any potential causative mutations. However, a single nucleotide polymorphism (SNP) located within the spliceosome attachment region in intron 8 of UROS is shown to segregate with the disease allele. Our study supports the hypothesis that CEP in cattle is caused by a mutation affecting UROS; however, additional functional studies are needed to identify the causative mutation.

Genomic regions associated with ventro-cranial chronic pleuritis in pig.

Ventro-cranial chronic pleuritis can be a result of pleuropneumonia and enzootic pneumonia. These diseases cause severe losses in intensive pig production worldwide, but host resistance is difficult to breed for. It could be beneficial to use marker-assisted selection, and a step towards this is to identify genomic regions associated with the trait. For this purpose, 7304 pigs from 11 boar families were analysed for associations between single nucleotide polymorphisms and ventro-cranial chronic pleuritis. The pigs were genotyped by the use of the iSelect Custom 7 K porcine SNP Chip. Quantitative trait loci (QTL), significant at the chromosome-wide level, were identified on Sus scrofa chromosomes (SSC) 2, 4, 11, 12 and 13 in four different boar families. The QTL on SSC 4 in family G was also significant at the genome-wide threshold according to Bonferroni correction. We have identified a number of candidate genes, but the causative mutations still need to be identified. Markers closely associated with the resistance traits have a strong potential for use in breeding towards animals with improved characteristics concerning ventro-cranial chronic pleuritis.

Genome-wide association mapping for female fertility traits in Danish and Swedish Holstein cattle.

A genome-wide association study was conducted using a mixed model analysis for QTL for fertility traits in Danish and Swedish Holstein cattle. The analysis incorporated 2,531 progeny tested bulls, and a total of 36,387 SNP markers on 29 bovine autosomes were used. Eleven fertility traits were analyzed for SNP association. Furthermore, mixed model analysis was used for association analyses where a polygenic effect was fitted as a random effect, and genotypes at single SNPs were successively included as a fixed effect in the model. The Bonferroni correction for multiple testing was applied to adjust the significance threshold. Seventy-four SNP-trait combinations showed chromosome-wide significance, and five of these were significant genome-wide. Twenty-four QTL regions on 14 chromosomes were detected. Strong evidence for the presence of QTL that affect fertility traits were observed on chromosomes 3, 5, 10, 13, 19, 20, and 24. The QTL intervals were generally smaller than those described in earlier linkage studies. The identification of fertility trait-associated SNPs and mapping of the corresponding QTL in small chromosomal regions reported here will facilitate searches for candidate genes and candidate polymorphisms.

MicroRNA identity and abundance in porcine skeletal muscles determined by deep sequencing.

MicroRNAs (miRNA) are short single-stranded RNA molecules that regulate gene expression post-transcriptionally by binding to complementary sequences in the 3' untranslated region (3' UTR) of target mRNAs. MiRNAs participate in the regulation of myogenesis, and identification of the complete set of miRNAs expressed in muscles is likely to significantly increase our understanding of muscle growth and development. To determine the identity and abundance of miRNA in porcine skeletal muscle, we applied a deep sequencing approach. This allowed us to identify the sequences and relative expression levels of 212 annotated miRNA genes, thereby providing a thorough account of the miRNA transcriptome in porcine muscle tissue. The expression levels displayed a very large range, as reflected by the number of sequence reads, which varied from single counts for rare miRNAs to several million reads for the most abundant miRNAs. Moreover, we identified numerous examples of mature miRNAs that were derived from opposite sides of the same predicted precursor stem-loop structures, and also observed length and sequence heterogeneity at the 5' and 3' ends. Furthermore, KEGG pathway analysis suggested that highly expressed miRNAs are involved in skeletal muscle development and regeneration, signal transduction, cell-cell and cell-extracellular matrix communication and neural development and function.

Refined candidate region specified by haplotype sharing for Escherichia coli F4ab/F4ac susceptibility alleles in pigs.

Infection of the small intestine by enterotoxigenic Escherichia coli F4ab/ac is a major welfare problem and financial burden for the pig industry. Natural resistance to this infection is inherited as a Mendelian recessive trait, and a polymorphism in the MUC4 gene segregating for susceptibility/resistance is presently used in a selection programme by the Danish pig breeding industry. To elucidate the genetic background involved in E. coli F4ab/ac susceptibility in pigs, a detailed haplotype map of the porcine candidate region was established. This region covers approximately 3.7 Mb. The material used for the study is a three generation family, where the founders are two Wild boars and eight Large White sows. All pigs have been phenotyped for susceptibility to F4ab/ac using an adhesion assay. Their haplotypes are known from segregation analysis using flanking markers. By a targeted approach, the candidate region was subjected to screening for polymorphisms, mainly focusing on intronic sequences. A total of 18 genes were partially sequenced, and polymorphisms were identified in GP5, CENTB2, APOD, PCYT1A, OSTalpha, ZDHHC19, TFRC, ACK1, MUC4, MUC20, KIAA0226, LRCH3 and MUC13. Overall, 227 polymorphisms were discovered in the founder generation. The analysis revealed a large haplotype block, spanning at least 1.5 Mb around MUC4, to be associated with F4ab/ac susceptibility.

Identification of QTL for dorso-caudal chronic pleuritis in 12 crossbred porcine families.

Pleuropneumonia is a major problem in pig production. At the time of slaughter, chronic pleuritis (CP) developed from pleuropneumonia is a common finding, and breeding for a reduced incidence of CP using marker-assisted selection (MAS) would be advantageous. Before applying MAS, quantitative trait loci (QTL) or markers associated with the prevalence of CP should be identified. In this study, 7470 pigs from crosses between 12 Danish Duroc boars and 604 sows (Danish Landrace × Danish Large White) were evaluated for CP located on the dorso-caudal part of the lungs. Quantitative trait loci were identified within boar families using both a Binomial logistic regression method and a chi-square test of association. Significant QTL for CP were detected on Sus scrofa chromosomes (SSC) 2, 8, 12, 13, 14 and 18 using both methods. One QTL on SSC 8 was also detected across families. For the QTL identified within families, the odds-ratio of having CP was approximately twice as high for the unfavourable allele compared to the favourable one. These QTL and closely linked markers show promise for the development of gene-specific markers associated with a reduced incidence of CP located on the dorso-caudal part of the lungs.

Effectiveness of microsatellite and SNP markers for parentage and identity analysis in species with low genetic diversity: the case of European bison.

The European bison (Bison bonasus) has recovered successfully after a severe bottleneck about 90 years ago but has been left with low genetic variability that may substantially hinder parentage and identity analysis. According to pedigree analysis, over 80% of the genes in the contemporary population descend from just two founder animals and inbreeding coefficients averaged almost 0.5, whereas microsatellite heterozygosity does not exceed 0.3. We present a comparison of the effectiveness of 17 microsatellite and 960 single nucleotide polymorphism (SNP) markers for paternity and identity analysis in the European bison. Microsatellite-based paternity and identity analysis was unsuccessful because of low marker heterozygosity and is not a practical approach in this species. Simulations using SNP markers suggest that 80-90 randomly selected loci, or just 50-60 of the most heterozygous loci, would be sufficient to ensure successful paternity and identity analysis in this species. For the purpose of standardizing future analysis, a panel of 50-60 bovine SNPs characterized by high heterozygosity and an even distribution in the genome could be selected. This panel of markers could be typed using VeraCode (Illumina) or similar SNP genotyping systems. The low cost of these SNP genotyping methods compared with a 16 locus microsatellite survey means that off-the-shelf SNP genotyping systems developed for domestic species represent powerful tools for genetic analysis in related species, and can be effective even in bottlenecked species in which heterozygosity of other markers such as microsatellites may be very low.

Circulating surfactant protein D is decreased in early rheumatoid arthritis: a 1-year prospective study.

Innate immune system abnormalities, e.g., mannan-binding lectin (MBL) genotype variants, have been demonstrated to modify the disease course of rheumatoid arthritis (RA). Surfactant protein D (SP-D) shares important structural and functional properties with MBL suggesting that SP-D may be an additional RA disease modifier. The Met11Thr polymorphism in the N-terminal part of SP-D is an important determinant for the SP-D serum level, but this polymorphism is also essential to the function and assembly into oligomers. We aimed to compare the serum levels of SP-D in a cohort of newly diagnosed untreated RA patients with healthy matched controls, and to investigate if there was an association to core measures of disease activity within the first year after disease onset. Secondly, we aimed to investigate whether the Met11Thr polymorphism was associated with RA. Serum SP-D was significantly lower in DMARD naive RA patients compared with healthy controls (P = 0.016). Median SP-D concentration at inclusion was 878 ng/ml (95% CI: 730-1033) and 1164 ng/ml (95% CI: 1093-1366) in RA patients and matched controls, respectively. SP-D increased during Methotrexate treatment (P < 0.0001), and at 1-year follow-up median SP-D was 1032 ng/ml (95% CI: 777-1255). SP-D levels did not correlate with traditional disease activity measures. The Thr11/Thr11 genotype and the Thr11 allele tended to be more frequent in RA patients. In conclusion, the low serum level of SP-D and the lack of correlation with traditional disease activity measures indicate that SP-D reflects a distinctive aspect in the RA pathogenesis.

Detection of quantitative trait loci in Danish Holstein cattle affecting clinical mastitis, somatic cell score, udder conformation traits, and assessment of associated effects on milk yield.

The aim of this study was to 1) detect QTL across the cattle genome that influence the incidence of clinical mastitis and somatic cell score (SCS) in Danish Holsteins, and 2) characterize these QTL for pleiotropy versus multiple linked quantitative trait loci (QTL) when chromosomal regions affecting clinical mastitis were also affecting other traits in the Danish udder health index or milk production traits. The chromosomes were scanned using a granddaughter design where markers were typed for 19 to 34 grandsire families and 1,373 to 2,042 sons. A total of 356 microsatellites covering all 29 autosomes were used in the scan. Among the across-family regression analyses, 16 showed chromosome-wide significance for the primary traits incidence of clinical mastitis in first (CM1), second (CM2), and third (CM3) lactations, and SCS. Regions of chromosomes 5, 6, 9, 11, 15, and 26 were found to affect CM and regions of chromosomes 5, 6, 8, 13, 22, 23, 24, and 25 affected SCS. Markers on chromosomes 6, 11, 15, and 26 can be used to perform marker-assisted selection on CM without a direct negative selection on milk yield, because no effects were detected on the milk traits. Comparing multi-trait models assuming either a pleiotropic QTL affecting 2 traits or 2 QTL each affecting 1 trait gave some evidence to distinguish between these models. For Bos taurus autosome 5, the most likely models were a pleiotropic QTL affecting CM2, CM3, and SCS, and a linked QTL affecting fat yield index. For Bos taurus autosome 9, the most likely model is a pleiotropic QTL affecting CM1 and CM2 at approximately 8 cM.

Porcine DJ-1: cloning of PARK7 cDNA, sequence comparison, expression analysis and chromosomal localization.

The PARK7 gene encodes a protein, DJ-1, with several functions such as protection of cells from oxidative stress, sperm maturation and fertilization and chaperone activity. Mutations in the PARK7 gene are associated with autosomal recessive early-onset Parkinson's disease (Parkinsonism). This work reports the cloning and analysis of the porcine (Sus scrofa) homologue of DJ-1. The porcine PARK7 cDNA was amplified by reverse transcriptase polymerase chain reaction (RT-PCR) using oligonucleotide primers derived from in silico sequences. The porcine PARK7 cDNA (SsPARK7) encodes a protein of 189 amino acids which shows a very high similarity to bovine (97%), to human (96%) and to canine (95%) DJ-1. Protein structure comparison of human and porcine DJ-1 sequences revealed that amino acid changes were few between the two species and not likely to alter DJ-1 structure and function. Quantitative real-time RT-PCR detection exhibited SsPARK7 mRNA expression in all analyzed porcine tissues, although at different levels. Furthermore, expression analysis showed that SsPARK7 transcripts could be detected early in embryo development in different brain regions. The PARK7 gene was demonstrated to be located on porcine chromosome 6. Single-nucleotide polymorphism (SNP) analysis revealed one SNP in the porcine PARK7 gene, giving rise to a silent mutation in exon 6.

The yeast type I topoisomerase Top3 interacts with Sgs1, a DNA helicase homolog: a potential eukaryotic reverse gyrase.

We have previously shown that cells mutant for TOP3, a gene encoding a prokaryotic-like type I topoisomerase in Saccharomyces cerevisiae, display a pleiotropic phenotype including slow growth and genome instability. We identified a mutation, sgs1 (slow growth suppressor), that suppresses both the growth defect and the increased genomic instability of top3 mutants. Here we report the independent isolation of the SGS1 gene in a screen for proteins that interact with Top3. DNA sequence analysis reveals that the putative Sgs1 protein is highly homologous to the helicase encoded by the Escherichia coli recQ gene. These results imply that Sgs1 creates a deleterious topological substrate that Top3 preferentially resolves. The interaction of the Sgs1 helicase homolog and the Top3 topoisomerase is reminiscent of the recently described structure of reverse gyrase from Sulfolobus acidocaldarius, in which a type I DNA topoisomerase and a helicase-like domain are fused in a single polypeptide.

Molecular dissection of interactions between Rad51 and members of the recombination-repair group.

Recombination is important for the repair of DNA damage and for chromosome segregation during meiosis; it has also been shown to participate in the regulation of cell proliferation. In the yeast Saccharomyces cerevisiae, recombination requires products of the RAD52 epistasis group. The Rad51 protein associates with the Rad51, Rad52, Rad54, and Rad55 proteins to form a dynamic complex. We describe a new strategy to screen for mutations which cause specific disruption of the interaction between certain proteins in the complex, leaving other interactions intact. This approach defines distinct protein interaction domains and protein relationships within the Rad51 complex. Alignment of the mutations onto the constructed three-dimensional model of the Rad51 protein reveal possible partially overlapping interfaces for the Rad51-Rad52 and the Rad51-Rad54 interactions. Rad51-Rad55 and Rad51-Rad51 interactions are affected by the same spectrum of mutations, indicating similarity between the two modes of binding. Finally, the detection of a subset of mutations within Rad51 which disrupt the interaction with mutant Rad52 protein but activate the interaction with Rad54 suggests that dynamic changes within the Rad51 protein may contribute to an ordered reaction process.

Detection of quantitative trait loci affecting lameness and leg conformation traits in Danish Holstein cattle.

Lameness is an important factor for culling animals. Strong legs and feet improve herd life of dairy cows. Therefore, many countries include leg and feet conformation traits in their breeding programs, often as early predictors of longevity. However, few countries directly measure lameness related traits to include these in a breeding program. Lameness indices in 3 different lactations and 5 leg conformation traits (rear legs side view, rear legs rear view, hock quality, bone quality, and foot angle) were measured on granddaughters of 19 Danish Holstein grandsires with 33 to 105 sons. A genome scan was performed to detect quantitative trait loci (QTL) based on the 29 autosomes using microsatellite markers. Data were analyzed across and within families for QTL affecting lameness and leg conformation traits. A regression method and a variance component method were used for QTL detection. Two QTL each for lameness in the first [Bos taurus autosome (BTA); BTA5, BTA26] and second (BTA19, BTA22) lactations were detected. For the 5 different leg conformation traits, 7 chromosome-wise significant QTL were detected across families for rear legs side view, 5 for rear legs rear view, 4 for hock quality, 4 for bone quality, and 1 for foot angle. For those chromosomes where a QTL associated with 2 different traits was detected (BTA1, BTA11, BTA15, BTA26, and BTA27), a multitrait-1-QTL model and a multitrait-2-QTL model were performed to characterize these QTL as single QTL with pleiotropic effects or distinct QTL.

Multitrait quantitative trait Loci mapping for milk production traits in danish Holstein cattle.

The aims of this study were (1) to confirm previously identified quantitative trait loci (QTL) on bovine chromosomes 6, 11, 14, and 23 in the Danish Holstein cattle population, (2) to assess the pleiotropic nature of each QTL on milk production traits by building multitrait and multi-QTL models, and (3) to include pedigree information on nongenotyped individuals to improve the estimation of genetic parameters underlying the random QTL model. Nineteen grandsire families were analyzed by single-trait (ST) and multitrait (MT) QTL mapping methods. The variance component-based QTL mapping model was implemented via restricted maximum likelihood (REML) to estimate QTL position and parameters. Segregation of the previously identified QTL was confirmed on bovine chromosomes 6, 11, and 14, but not on 23. A highly significant (1% chromosome-wise level) QTL was found on chromosome 6, between 37 and 73 cM. This QTL had a strong effect on protein percentage (PP) and fat percentage (FP) according to ST analyses, and effects on PP, FP, milk yield (MY), fat yield (FY), and protein yield (PY) in MT analyses. A QTL affecting PP was detected on chromosome 11 (at 70 cM) using ST analysis. The MT analysis revealed a second QTL (at 67 cM) approaching significance with an effect on MY. The ST analysis identified a QTL for MY and FP on chromosome 14, between 10 and 24 cM. The extended pedigree (nongenotyped animals) was included to estimate genetic parameters underlying the random QTL model; that is, additive polygenic and QTL variances. In general, the estimates of the QTL variance components were smaller but more precise when the extended pedigree was considered in the analysis.

Detection of genetic variation affecting milk coagulation properties in Danish Holstein dairy cattle by analyses of pooled whole-genome sequences from phenotypically extreme samples (pool-seq).

Rennet-induced milk coagulation is an important trait for cheese production. Recent studies have reported an alarming frequency of cows producing poorly coagulating milk unsuitable for cheese production. Several genetic factors are known to affect milk coagulation, including variation in the major milk proteins; however, recent association studies indicate genetic effects from other genomic regions as well. The aim of this study was to detect genetic variation affecting milk coagulation properties, measured as curd-firming rate (CFR) and milk pH. This was achieved by examining allele frequency differences between pooled whole-genome sequences of phenotypically extreme samples (pool-seq).. Curd-firming rate and raw milk pH were measured for 415 Danish Holstein cows, and each animal was sequenced at low coverage. Pools were created containing whole genome sequence reads from samples with "extreme" values (high or low) for both phenotypic traits. A total of 6,992,186 and 5,295,501 SNP were assessed in relation to CFR and milk pH, respectively. Allele frequency differences were calculated between pools and 32 significantly different SNP were detected, 1 for milk pH and 31 for CFR, of which 19 are located on chromosome 6. A total of 9 significant SNP, which were selected based on the possible function of proximal candidate genes, were genotyped in the entire sample set ( = 415) to test for an association. The most significant SNP was located proximal to , explaining 33% of the phenotypic variance. , coding for κ-casein, is the most studied in relation to milk coagulation due to its position on the surface of the casein micelles and the direct involvement in milk coagulation. Three additional SNP located on chromosome 6 showed significant associations explaining 7, 3.6, and 1.3% of the phenotypic variance of CFR. The significant SNP on chromosome 6 were shown to be in linkage disequilibrium with the SNP peaking proximal to ; however, after accounting for the genotype of the peak SNP within this QTL, significant effects (-value < 0.1) could still be detected for 2 of the SNP accounting for 2 and 1% of the phenotypic variance. These 2 interesting SNP were located within introns or proximal to the candidate genes-solute carrier family 4 (sodium bicarbonate cotransporter), member 4 () and LIM and calponin homology domains 1 (), respectively-making them interesting targets for further analysis.