Abstract
Simple SummaryMastitis is a worldwide diffused disease usually treated with an excessive use of antibiotics. Therefore, antimicrobial resistance is an important issue to be addressed by scientists. One of the possible solutions to decrease the use of drugs is genetic selection of resistant animals, that is, individuals that can be more resistant to mastitis. In our survey we analyzed Single Nucleotide Polymorphisms (SNPs) in genes known to be involved in both infection resistance and immune system activity. We found a group of SNPs that can be associated to mastitis related phenotypes (namely SCS) and that can be used for selecting resistant animals. An efficient selection is able to improve both animal welfare and quality and safety of animal productsMastitis is an infectious disease affecting the mammary gland, leading to inflammatory reactions and to heavy economic losses due to milk production decrease. One possible way to tackle the antimicrobial resistance issue stemming from antimicrobial therapy is to select animals with a genetic resistance to this disease. Therefore, aim of this study was to analyze the genetic variability of the SNPs found in candidate genes related to mastitis resistance in Holstein Friesian bulls. Target regions were amplified, sequenced by Next-Generation Sequencing technology on the Illumina® MiSeq, and then analyzed to find correlation with mastitis related phenotypes in 95 Italian Holstein bulls chosen with the aid of a selective genotyping approach. On a total of 557 detected mutations, 61 showed different genotype distribution in the tails of the deregressed EBVs for SCS and 15 were identified as significantly associated with the phenotype using two different approaches. The significant SNPs were identified in intergenic or intronic regions of six genes, known to be key components in the immune system (namely CXCR1, DCK, NOD2, MBL2, MBL1 and M-SAA3.2). These SNPs could be considered as candidates for a future genetic selection for mastitis resistance, although further studies are required to assess their presence in other dairy cattle breeds and their possible negative correlation with other traits.
Highlights
Mastitis is an infectious disease that affects the mammary gland of cattle, leading to an inflammatory reaction and to negative economic consequences due to a marked decrease in milk production [1]
Other genes are included in the sequenced regions of the bovine genome assembly: Pentraxin 3 (PTX3) gene is included in a region within the ventricular zone expressed PH domain homolog 1 gene (VEPH1) and the collectin surfactant protein A (SP-A) gene (SFPTA1) is located downstream MBL1
Wang et al [43], using a Genome Wide Association Study (GWAS) approach found a significant single nucleotide polymorphisms (SNPs) in SAA2 gene, indicating an important role of the superfamily of these apolipoproteins. These results suggest that, just like CXCR1 and Deoxycytidine kinase (DCK) genes, MBL1, MBL2, Nucleotide binding oligomerization domain containing 2 (NOD2) and M-SAA3.2 genes could be eligible as candidate genes for genetic selection of mastitis resistant cows
Summary
Mastitis is an infectious disease that affects the mammary gland of cattle, leading to an inflammatory reaction and to negative economic consequences due to a marked decrease in milk production [1]. This infection is usually caused by microorganisms penetrating the mammary gland via teat canal [2]: pathogens can be transmitted either between cows (e.g., Staphylococcus aureus) or picked up from the environment (e.g., Escherichia coli) [3]. New genetic approaches to find markers able to allow a faster and more accurate selection are requested, with two potential available candidates: genome scanning and single nucleotide polymorphisms (SNPs) in candidate genes [6]. The SNP approach in candidate genes involved in organism recognition, leukocyte recruitment, pathogen elimination and resolution seem to be more direct and reliable
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