LAUSR

Feeding high-grain diets to dairy cows increases concentrations of acute phase proteins in peripheral blood. This inflammatory response can be reduced by supplementation with Saccharomyces cerevisiae fermentation products (SCFP). It is not clear which cytokines drive this inflammatory response, which organs are inflamed, and how these processes are affected by SCFP. The objectives of this study were to investigate if grain-induced SARA increases the concentrations of the cytokines IL-1β in peripheral blood, and of the inflammatory marker myeloperoxidase (MPO) in rumen papillae of lactating dairy cows, and if these concentrations are affected by SCFP. Thirty-two lactating Holstein dairy cows were randomly assigned to four treatment groups (n = 8) that received a TMR (34.9 %DM NDF, 18.6 %DM starch) supplemented with 1) 140 g/d of ground corn (Control), 2) 126 g/d corn and 14 g/d of Diamond V Original XPCTM (XPC), 3) 121 g/d corn and 19 g/d Diamond V NutriTek® (NTL), and 4) 102 g/d corn and 38 g/d of Diamond V NutriTek® (NTH). SARA challenges were conducted during wk 5 (SARA1) and 8 (SARA2) of lactation by replacing 20% of the base TMR with pellets containing 50% barley and 50% wheat. Blood samples were taken weekly between wk 4 (preSARA1) and wk 9 (postSARA2) for the analysis of IL-1β. Rumen papillae samples were taken during wk 3 (preSARA1) and wk 9 (postSARA2) for the measurement of MPO. SCFP treatment did not affect the concentrations of IL-1β, but the SARA challenges increased this concentration moderately from 9.0 to 12.3 pg/mL (P < 0.05). The concentration of MPO did not differ between preSARA1 and postSARA2, and these concentrations were not affected by SCFP. Results suggest that IL-1β may drive the acute phase response during the SARA challenges, and that these challenges did not cause inflammation of rumen papillae.