Submitted to: Research Workers in Animal Diseases Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 9/9/2004
Publication Date: 11/15/2004
Citation: Eicher, S.D., Johnson, T.A., Cary, D.C., Patterson, J.A. 2004. Yeast cell-wall products plus ascorbic acid: potential immune modulators for neonatal calves. Proceedings of the Conference of Research Workers in Animal Diseases. p. 131.
Technical Abstract: Salmonella dublin frequently causes morbidity and mortality in calves during the neonatal period. The objective of this study was to examine the efficacy of ß-glucan with ascorbic acid, for protection against a S. dublin challenge. Thirty-eight calves, 3-10 days-of-age were randomly assigned to: A yeast cell-wall product containing 2% beta-glucan plus ascorbic acid (EP); a purified B-glucan plus ascorbic acid (BG); and a control (CTL, no supplements). Treatments were delivered in feed. On day (d) 21, all calves received an oral challenge of 4.28 X 10*8 CFU of S. dublin. Blood was collected on d 21, 24, 28, 32, 35, and 42. Differential counts were determined using the QBC VetAutoRead analyzer. Whole blood phagocytosis and oxidative burst and CD18 expression was determined for blood leukocytes, by flow cytometry. An aliquot of the whole blood was used for RNA extraction and real-time RT-PCR to evaluate relative expression of toll-like receptor (TLR) 2 and TLR4. The ability of neutrophils to phagocytize was enhanced (P< .05) after the challenge for all treatments (d 24), with no differences among the treatments until at d 32, when the EP group returned to lower mean fluorescence values than CTL. In contrast, the percentage of cells positive for phagocytosis at d 35 tended (P<.10) to be less for neutrophils from the calves fed BG than CTL. CD18 did not differ among treatments after the challenge. There were no differences among treatments after the challenge for RNA expression of TLR2 and TLR4 in blood leukocytes. However, within treatment, the BG treatment increased (P<.05) TLR4 expression from d 21 to d 24. These data show that neonatal calf TLR 2 and 4 were not responsive to in vivo S. dublin exposure. This lack of immune response may result in the increased susceptibility of the neonate to this pathogen, and demonstrates the importance of the neutrophil population during this time. This information will impact future research by allowing a focus on the cells that are the most responsive at this early age and to know the weak link of the developing immune system to target other potential immunomodulators.