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-alpha response, CD14+ monocyte number, and CD14 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.

Commercially available antibodies to human tumour necrosis factor-alpha tested for cross-reactivity with ovine and bovine tumour necrosis factor-alpha using flow cytometric assays.

A thorough understanding of the immune system, including the role of different cytokines, during inflammatory diseases in ruminants could lead to the development of new diagnostic methods and treatments. Tumour necrosis factor-alpha (TNF-alpha) is an important cytokine in the onset of the inflammatory responses. Unfortunately, the number of studies on cytokines, like TNF-alpha, in ruminants is limited due to a lack of species-specific reagents. As cytokines have remained rather conserved during evolution, cross-reactivity between animal species may occur. Therefore, the aim of the present study was to investigate 5 commercially available antibodies against human TNF-alpha for their ability to cross-react with ovine and/or bovine TNF-alpha, using a bead-based flow cytometric method. Two of the antibody clones (Mab 11 and 6401.1111) showed cross reactivity with ovine recombinant TNF-alpha in concentrations above 2.5 ng/ml. However, none of the antibodies detected TNF-alpha in bovine milk, or serum containing known concentrations of bovine TNF-alpha, as earlier determined with ELISA. The results could be due to inability of the antibodies to cross-react between species, but quenching of the signal by matrix proteins might also have lowered the response.