Association ofCXCR1polymorphisms with apoptosis, necrosis and concentration of milk neutrophils in early lactating dairy heifers

Associations between polymorphisms in the candidate geneCXCR1, encoding the chemokine (C-X-C motif) receptor 1, and udder health have been identified before. In the present study, associations between theCXCR1genotype (whole coding region) and apoptosis, necrosis, and concentration of milk polymorphonuclear neutrophilic leukocyte (PMNL) of 292 quarters belonging to 73 early lactating dairy heifers were studied. In uninfected quarters, % milk PMNL apoptosis was higher in c.980GG heifers [least squares means (LSM) 27%] compared to c.980AG heifers (LSM 16%), whereas in infected quarters, % milk PMNL apoptosis was higher in c.642GG heifers (LSM 29%) compared to c.642AG heifers (LSM 18%). Differences in milk PMNL concentration between infected and uninfected quarters were smaller in c.980AG heifers than in c.980GG heifers. An association between theCXCR1genotype and necrosis of milk PMNL could not be demonstrated. Results indicate thatCXCR1polymorphisms influence viability and concentration of milk PMNL and provide a foundation for future research.