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Abstract
These studies were designed with the intent to evaluate the impact of milk yield genotype on ex-vivo cytokine response to stimulation of whole blood with Gram-negative and Gram-positive antigens. The unselected Holsteins (UH) utilized have remained genetically stable since 1964 and produce less than 4,500 kg/lactation than their contemporary (CH) herdmates. This unique comparison allows for the assessment of selection on immune response. During the transition period, UH and CH cows exhibited a dose-dependent cytokine response to lipopolysaccharide (LPS) and lipoteichoic acid (LTA) that decreased as day in milk increased. The UH cows demonstrated a more robust immune response and had a less negative energy balance during the periparturient period when compared to the CH. The more negative energy balance in CH cows did not impact the genotype differences demonstrated in cytokine responses. The UH cows also exhibited a greater cytokine response to heat-killed Gram-negative and Gram-positive bacteria. The response to LPS was highly correlated to the response to LTA and to Gramnegative bacteria in both genotypes. These differences in ex-vivo pro-inflammatory cytokine concentrations in plasma indicate UH have a more robust immune response when compared to CH cows, consistent with previous efforts by our lab and collaborators. The results indicate selection from the mid-1960s has decreased ex-vivo whole blood cytokine response of CH cows to Gram-negative and Gram-positive antigens.