Association between CXCR1 gene polymorphisms and udder health in dairy heifers

Mastitis is highly prevalent in periparturient heifers, causing substantial economic losses when major pathogens are involved. Effective prevention of heifer mastitis relies on reducing the infection pressure as well as on optimizing the host resistance. Marker assisted selection against certain disadvantageous genotypes could offer possibilities to enhance mastitis resistance. The main objective of this study was to screen CXCR1 for polymorphisms and to analyze their association with udder health during first lactation. This potential candidate gene encodes the homonymous receptor binding interleukin 8, a crucial chemokine in the innate immunity of the mammary gland. Eighty-six heifers originating from 20 Belgian farms were genotyped. Associations between CXCR1 genotype and quarter intramammary infection (IMI) status in early lactation, quarter somatic cell count (SCC) in early lactation and composite SCC during first lactation, respectively, were tested. Fifteen polymorphisms were detected of which 10 have not been described before. Numerical differences, although not significant differences in SCC in early lactation and during lactation by CXCR1 genotype were observed. However, IMI status in early lactation was found to be associated with the polymorphism at position +642 (P < 0.05). Additionally, the polymorphism at position +982 tended (P < 0.1) to be associated with pathogen group specific IMI. Heifers with genotype GG at this position appeared to be less resistant to major pathogens. Results in this study are promising and stimulate to further elucidate the role of CXCR1 in mastitis susceptibility. Selection against certain CXCR1 genotypes might be an interesting tool for prevention of heifer mastitis