Effects of diet energy density and milking frequency in early lactation on tumor necrosis factor-alpha responsiveness in dairy cows

A whole blood stimulation assay (WBA) with Escherichia coli lipopolysaccharide (LPS) and an enzyme-linked immunosorbent assay (ELISA) were established to measure the production of tumor necrosis factor-alpha (TNF-alpha) in bovine plasma. The assays were used to study the effect of time around parturition, and diet energy density, and milking frequency on TNF-alpha responsiveness of dairy cows in early lactation. Forty cows were included in a 2 x 2 factorial block design. One factor was high (H) versus low (L) diet energy density and the other factor was two versus three daily milkings. Blood samples were collected in weeks -3, - 1, 2, 3, 5, 9, and 13 around parturition, and investigated for the TNF-alpha production ex vivo and CD14+ monocytes. The TNF-a response, CD 14+ monocyte number, and CD 14 expression level on monocytes were significantly increased in the weeks close to parturition. However, dips of varying sizes were observed for the measured parameters in week 3 after calving. Diet and milking frequency had no effect on the TNF-alpha response ex vivo or CD14 expression level on monocytes, but cows fed diet H had significantly higher numbers of CD14+ monocytes than cows fed diet L. The WBA with LPS was a fast reliable method for repeated measurements of TNF-alpha responsiveness in cattle. Previous findings of increased TNF-alpha responses in periparturient cows were confirmed, whereas diet energy concentration and milking frequency had no effect on the TNF-alpha responsiveness in early lactation. (c) 2004 Elsevier B.V. All rights reserved.