Use of gene profiling to evaluate the effects of a feed additive on immune function in periparturient dairy cattle.

Objectives were to investigate mechanisms by which a nutritional supplement alters immunity in dairy cattle. Our hypothesis was that feeding this product to dairy cattle altered neutrophil gene expression. Eight periparturient Jersey cattle were randomly assigned to one of two treatments: control and treated. Control animals were fed a dry cow ration for 1 month prior to calving. The treated cows were fed the same ration supplemented with OmniGen-AF. Following calving, blood samples were taken and neutrophils were prepared after which RNA was extracted. Gene expression in neutrophils of treated versus control-fed animals was then assessed using bovine-total leukocyte (BOTL-5) arrays. Eighteen genes were differentially regulated in the experimental group and of these, twice as many were up-regulated as down-regulated. Patterns of changes indicated that the additive might alter neutrophil apoptosis, signaling and sensitivity. Two of the regulated genes [interleukin-1beta converting enzyme (ICE) and interleukin-4 receptor (IL-4R)] were investigated in more detail using quantitative reverse transcriptase-polymerase chain reaction (QRT-PCR). Each was found to be elevated by the feeding of experimental product. Increased expression of ICE indicates potential for enhanced neutrophil expression of interleukin-1beta (IL-1beta), a cytokine which plays roles in the inflammatory response and which stimulates adaptive immunity following innate immune activation. Altered expression of IL-4R indicates potential for changes in neutrophil apoptosis. The experiment identified mechanisms by which the additive altered neutrophil gene expression. While many nutrients support the immune system, we have shown that a non-traditional nutritional approach may also have utility in modulating immune function.