The innate immune response plays an important role in the course of bacterial infections. Innate immunity effectiveness relies on the expression of many genes, connected, among others, to the activity of neutrophils. Interleukin 8 (IL-8) receptor α, coded by the CXCR1 gene, is present on the neutrophil surface and binds pro-inflammatory IL-8 with high affinity. This is why the bovine CXCR1 gene carries a potential for use as a dairy cattle mastitis marker. To date, several studies on the CXCR1 polymorphism brought out contradictory results. The aim of this study was to analyse the association between two SNPs of the CXCR1 gene, which is potentially important for the protein function and animal phenotype for mastitis susceptibility. A total of 554 Polish Holsteins were genotyped, and 140 among them were bacteriologically tested. The differences between animals carrying different genotypes and haplotypes of CXCR1 in test day somatic cell count (SCC) and Staphylococcus aureus mastitis susceptibility were estimated. We found that test day SCC was significantly related to CXCR1+472 SNP but not to CXCR1+735 SNP. No statistically significant association between CXCR1 polymorphism and susceptibility to S. aureus mastitis was found in the studied herd.

Mastitis is one of the most important mammary gland diseases impacting lactating animals. Resistance to this disease could be improved by breeding. There are several selection methods for mastitis resistance. To improve the natural genetic resistance of cows in succeeding generations, current breeding programmes use somatic cell count and clinical mastitis cases as resistance traits. However, these methods of selection have met with limited success. This is partly due to the complex nature of the disease. The limited progress in improving udder health by conventional selection procedures requires applying information on molecular markers of mastitis susceptibility in marker-assisted selection schemes. Mastitis is under polygenic control, so there are many genes that control this trait in many loci. This review briefly describes genome-wide association studies which have been carried out to identify quantitative trait loci associated with mastitis resistance in dairy cattle worldwide. It also characterizes the candidate gene approach focus on identifying genes that are strong candidates for the mastitis resistance trait. In the conclusion of the paper we focus our attention on future research which should be conducted in the field of the resistance to mastitis.

Lactoferrin gene (LF) is regarded as one of the potential markers of mastitis susceptibility/resistance in dairy cattle. The study’s aim was therefore, to investigate the feasibility of two single nucleotide polymorphisms (SNP), placed in the 5′-flanking region and 3′-untranslated region of the LF gene, to serve as mastitis markers. The associations between these SNP and the expression of LF, both on mRNA and protein level, were estimated in the milk of Polish Holstein-Friesian cows. The relationships between polymorphisms and cows’ estimated breeding values (EBV) for somatic cell count were also calculated. It was shown that both polymorphisms have a significant impact on lactoferrin content in milk, and that LF+32 SNP is associated with the cow’s EBV for somatic cell count. No association between SNP chosen for the study and lactoferrin mRNA abundance in milk somatic cells was observed. We propose LF+32 SNP for a molecular marker of mastitis resistance in dairy cows.

The study aimed at clarifying the problem of the hitherto contradictory results regarding usefulness of BoLA-DRB3 locus as a marker in selection against mastitis and for milk yield. Treating the BoLA-DRB3 locus effect as random was proposed in place of considering it fixed. Somatic cell counts and milk yields recorded monthly on a test day (22,424) of 619 Polish Holstein cows genotyped for BoLA-DRB3 were analysed with an animal model including a random effect for genotype at this locus. The BoLA-DRB3 alleles were defined as restriction patterns obtained with three endonucleases. Two alternative BoLA-DRB3 additive genotype (co)variance structures were constructed for 161 genotypes recorded. One was based on the allelic similarity of the genotypes resulting in element values of 0 (no common allele), 0.5 (one allele in common), and 1 (diagonal). The other considered restriction site similarity (up to 3 in 1 allele) giving element values of 0 (no common restriction sites) and then increasingly in steps of 1/6 up to 6/6 (diagonal), where the numerator represents the number of common sites between genotypes. The DRB3 variance component for the natural logarithm of somatic cell count did not exceed 0.006 of the polygenic additive component or 0.003 for milk yield. Hence, unless we fail to detect the causative site or to properly define traits being the projection of a site, the effect of the genotype at the BoLA-DRB3 locus does not explain variation in somatic cell count and milk yield at a degree expected of a genetic marker.

Acyl-CoA:diacylglycerol acyltransferase-1 (DGAT-1) is a key enzyme involved in triglyceride synthesis. DGAT-1 gene is located in the centromeric region of the bovine chromosome (BTA) 14 and considered polymorphism was identified as a candidate gene for milk and meat QTL. One of mutations which is substitution AA → GC in exon 8 causes an amino acid change in the product. The effect of the lysine/alanine (K232A) diallelic polymorphism on meat production traits has been studied. 156 young Black-and-White (Friesian) bulls were genotyped. The association between diacylglycerol acyltransferase polymorphism and slaughter performance and meat technology analysis were examined. Moreover the fatty acid profile (C12-C20:5) including CLA in the sample of longissimus dorsi (LD) muscle was evaluated. Differences (P ≤ 0,05) were found between genotypes in slaughtering performance traits as well as fat and valuable cuts content and meat-fat ratio. The significant difference occurred also in the water holding capacity. Heterozygous individuals AA:GC were characterized by the greatest values compared with homozygous ones. Bulls of DGAT-1 genotype GC:GC showed significantly higher (P ≤ 0,05) content of lauric acid in LD muscle and heterozygous animals differ in CLA content with homozygous AA:AA.