Effect of dietary supplementation on the antimicrobial activity of blood leukocytes isolated from Holstein heifers.

The purpose of this investigation was to evaluate the effect of an immunostimulating feed supplement (OmniGen-AF®) on the antimicrobial properties of blood leukocytes in dairy heifers in an attempt to prevent mastitis. Blood leukocytes from supplemented and unsupplemented controls were used. Phagocytic activity and reactive oxygen species (ROS) production were studied on d 0 (prior to feed supplementation) and on days 30 and 60 after supplementation. L-selectin and IL-8R mRNA expressions on blood leukocytes were evaluated on d 0 (prior to feed supplementation) and monthly thereafter for 15 mo. On d 30 after supplementation, neutrophils from treated heifers exhibited greater binding and internalization of Escherichia coli and greater ROS production compared with unsupplemented controls. L-selectin mRNA expression was increased in supplemented heifers vs. controls; however, IL-8R mRNA expression was not different. Results support the continued study of dietary supplementation as an additional management tool to enhance udder health in dairy heifers.