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Bovine mastitis continues to be the most detrimental factor for profitable dairying. Recent research conducted within our laboratory has identified a genetic marker in the CXCR2 gene associated with mastitis susceptibility. The objective of the present study was to evaluate the migratory ability of neutrophils from cows with different CXCR2 ؉777 genotypes. Neutrophils isolated from peripheral blood of 30 Holstein cows were tested for in vitro migration and adhesion molecule expression. Cows with the CC or GC genotype at CXCR2 ؉777 showed significantly lower neutrophil migration to recombinant human interleukin-8 (rhIL-8) than cows with the GG genotype (P < 0.05). Cows with the CC genotype at CXCR2 ؉777 also showed decreased neutrophil migration to zymosan-activated serum compared to these same cows (P < 0.05). Decreased upregulation of CD18 expression was observed after stimulation with rhIL-8 in cows expressing the CXCR2 ؉777 CC genotype compared to cows expressing the GG genotype (P < 0.05). A similar trend was observed for CD11b (P < 0.10). However, no difference in CD62 downregulation was observed with respect to genotype. These results provide initial evidence for a phenotypic association between a single nucleotide polymorphism and neutrophil function in dairy cows, as well as potential insight into specific mechanisms affected in cows more susceptible to mastitis.