ABSTRACT:The study included 124 Polish Black-and-White dairy cows of various share of the Holstein-Friesian (HF) breed. Lactoferrin (LTF) gene polymorphism was obtained with PCR-RFLP method using EcoRI enzyme. Two alleles of LTF, A and B, were found in the studied population. Their frequencies were 67.74% and 32.56%, respectively. The alleles controlled the occurrence of three genotypes: AA, BB and AB, of frequencies equal to 37.90%, 2.42% and 59.68%, respectively. It was established that statistically significant associations exist between the somatic cell count (SCC) and LTF genotype, lactation month and parity as well as the HF gene share. No significant association was found between somatic cell count and season. The highest somatic cell count (transformed to a logarithmic scale) was found in milk of the AB genotype, whereas the lowest one was found in cows of the AA genotype.

BackgroundOne major problem in dairy cattle husbandry is the prevalence of udder infections. In today’s breeding programmes, top priority is being given to making animal evaluation more cost-effective and reliable and less time-consuming. We proposed tumor necrosis factor α (TNF-α), lactoferrin (LTF) and macrophage-expressed lysozyme (mLYZ) genes as potential DNA markers in the improvement of immunity to mastitis.This study included 588 Polish Holstein-Friesian cows kept on one farm located in the north-western region of Poland. All clinical cases of mastitis in the herd under study were recorded by a qualified veterinarian employed by the farm. The following indicators were applied to determine udder immunity to mastitis in the cows under study: morbidity rate (MR), duration of mastitis (DM) and extent of mastitis (EM). TNF-α, mLYZ and LTF genotypes were identified by real-time PCR method, using SimpleProbe technology. Due to the very low frequency of mLYZ allele T, the gene was excluded from further analysis.A statistical analysis of associations between TNF-α and LTF genes and immunity to mastitis were performed using three models: 1) a parity-averaged model including only additive effects of the genes; 2) a parity-averaged model including both additive and epistatic effects of the genes; and 3) a parity-specific model including only additive effects of the genes.ResultsWith the first and second models it was revealed that the genes effects on the applied indicators of immunity to mastitis were non-significant whereas with the third one the effects were found to be statistically significant. Particularly noteworthy was the finding that the effects of TNF-α and LTF varied depending on age (parity). The alleles which were linked to high immunity to mastitis in lower parities appeared to be less favourable in higher parities.ConclusionsThese interactions might be related to inflamm-ageing, that is an increased susceptibility to infection due to immune system deregulation that progresses with age. Such pattern of interactions makes it impossible to use the genes in question in marker-assisted selection aimed at reducing heritable susceptibility to mastitis. This is because the immune mechanisms behind resistance to infections proved to be too complex.

Mastitis is an inflammatory disease of the mammary gland, which has a significant economic impact and is an animal welfare concern. This work examined the association between single nucleotide polymorphisms (SNPs) and copy number variations (CNVs) with the incidence of clinical mastitis (CM). Using information from 16 half-sib pairs of Holstein-Friesian cows (32 animals in total) we searched for genomic regions that differed between a healthy (no incidence of CM) and a mastitis-prone (multiple incidences of CM) half-sib. Three cows with average sequence depth of coverage below 10 were excluded, which left 13 half-sib pairs available for comparisons. In total, 191 CNV regions were identified, which were deleted in a mastitis-prone cow, but present in its healthy half-sib and overlapped in at least nine half-sib pairs. These regions overlapped with exons of 46 genes, among which APP (BTA1), FOXL2 (BTA1), SSFA2 (BTA2), OTUD3 (BTA2), ADORA2A (BTA17), TXNRD2 (BTA17) and NDUFS6 (BTA20) have been reported to influence CM. Moreover, two duplicated CNV regions present in nine healthy individuals and absent in their mastitis-affected half-sibs overlapped with exons of a cholinergic receptor nicotinic α 10 subunit on BTA15 and a novel gene (ENSBTAG00000008519) on BTA27. One CNV region deleted in nine mastitis-affected sibs overlapped with two neighbouring long non-coding RNA sequences located on BTA12. Single nucleotide polymorphisms with differential genotypes between a healthy and a mastitis-affected sib included 17 polymorphisms with alternate alleles in eight affected and healthy half-sib families. Three of these SNPs were located introns of genes: MET (BTA04), RNF122 (BTA27) and WRN (BTA27). In summary, structural polymorphisms in form of CNVs, putatively play a role in susceptibility to CM. Specifically, sequence deletions have a greater effect on reducing resistance against mastitis, than sequence duplications have on increasing resistance against the disease.

Despite the growing number of sequenced bovine genomes, the knowledge of the population-wide variation of sequences remains limited. In many studies, statistical methodology was not applied in order to relate findings in the sequenced samples to a population-wide level. Our goal was to assess the population-wide variation in DNA sequence based on whole-genome sequences of 32 Holstein–Friesian cows. The number of SNPs significantly varied across individuals. The number of identified SNPs increased with coverage, following a logarithmic curve. A total of 15,272,427 SNPs were identified, 99.16 % of them being bi-allelic. Missense SNPs were classified into three categories based on their genomic location: housekeeping genes, genes undergoing strong selection, and genes neutral to selection. The number of missense SNPs was significantly higher within genes neutral to selection than in the other two categories. The number of variants located within 3′UTR and 5′UTR regions was also significantly different across gene families. Moreover, the number of insertions and deletions differed significantly among cows varying between 261,712 and 330,103 insertions and from 271,398 to 343,649 deletions. Results not only demonstrate inter-individual variation in the number of SNPs and indels but also show that the number of missense SNPs differs across genes representing different functional backgrounds.

Milk components originating from blood plasma substrates are synthesized in epithelial cells of the mammary gland. Milk lipids are synthesized from fatty acids which bind to specific proteins – FABPs (fatty acid binding proteins). FABPs are a family of small cytoplasmic proteins; nine members of the family have been identified so far (FABP1–FABP9) (Chmurzyńska et al., 2006). Their main roles include fatty acid uptake, transport and metabolism. FABPs can modulate the fatty acid concentration in cells and therefore they affect different cellular processes, especially lipid metabolism. FABP3 and FABP4 are present in tissues with a high demand for fatty acids, such as heart muscle, skeletal muscles, lactating mammary gland, liver or adipose tissue (Roy et al., 2003). FABP3 gene was mapped to bovine chromosome 2 (Calvo et al., 2004), where QTLs affecting milk fat yield and content were described (Khatkar et al., 2004). FABP4 gene was mapped to BTA14 (Michal et al., 2006), which is very rich in QTLs for milk production traits (Khatkar et al., 2004). Fatty acid transport is assisted by the specific proteins called FATPs (fatty acid transport proteins). This protein group includes SLC27A3 (solute carrier family 27, member 3). It belongs to the family of proteins that facilitate long-chain fatty acid transport across the cytoplasmic membrane. Another protein with similar functions is ANXA9 (annexin A9), the member of Ca2+ and phospholipid-binding protein family (Calvo et al., 2006b). Genes encoding SLC27A3 and ANXA9 were mapped to chromosome 3, within the region where QTLs for milk fat content and the other milk traits have been mapped. Both of the above-mentioned genes are expressed in the mammary gland (Calvo et al., 2006b). The polymorphic sites (SNPs – single nucleotide polymorphisms) within the bovine FABP3, FABP4, SLC27A3 and ANXA9 genes were identified (Wu et al., 2005; Calvo et al., 2006b; Michal et al., 2006; Cho et al., 2008). Associations between SNPs in these genes and milk production traits in cattle have not been reported so far. However, polymorphism in the FABP4 gene has been significantly associated with carcass traits in cattle (Michal et al., 2006; Cho et al., 2008). Due to their expression sites, physiological properties and chromosomal localisation, the described genes might be considered as candidate genes for milk production traits. The aim of this study was to determine allele and genotype frequencies and to establish possible associations between the ANXA9, SLC27A3, FABP3 and FABP4 SNPs, and selected milk traits in Jersey cows.