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Feeding Saccharomyces cerevisiae fermentation products modulates immune function and reduces the severity of bovine respiratory syncytial virus infection in preweaned calves.

J. McGill

Events

06-23-2020

Abstract:

188
Feeding Saccharomyces cerevisiae fermentation products modulates immune function and reduces the severity of bovine respiratory syncytial virus infection in preweaned calves.
A. Mahmoud1,2, J. Slate1, S. Hong1, I. Yoon3, J. McGill*1. 1Iowa State University, Department of Veterinary Microbiology and Preventive Medicine Ames, IA, 2Veterinary Quarantine of Alexandria, General Organization for Veterinary Services, Ministry of Agriculture and Land Reclamation Alexandria, Egypt, 3Diamond V Cedar Rapids, IA.

Bovine respiratory disease (BRD) is a leading cause of mortality in preweaned dairy calves and weaned dairy heifers. Given increasing concerns related to the development of antimicrobial resistance, there is interest in identifying alternative strategies which can be used to reduce the impact of BRD. The objective of this study was to determine the effects of oral supplementation with Saccharomyces cerevisiae fermentation products (SCFP; SmartCare and NutriTek; Diamond V) on the outcome of bovine respiratory syncytial virus (BRSV) infection in preweaned dairy calves. Twenty-four, 1—2 d old calves were assigned 2 groups (12/group): 1) control, base milk replacer and calf starter; or 2) SCFP treated, milk replacer with 1 g/d SmartCare and calf starter top-dressed with 5 g/d NutriTek. Calves were challenged with ~104 (Median Tissue Culture Infectious Dose, TCID50) BRSV on d 21. Calves were monitored for clinical signs. Nasal swabs were collected to monitor virus shedding. Peripheral blood and bronchoalveolar lavage (BAL) samples were collected for immunologic analyses. Calves were euthanized on d 10 post infection to evaluate gross lung pathology and pathogen load in the lung tissue. Following BRSV infection, calves receiving SCFP had significantly reduced clinical disease scores compared with controls (P = 0.030); reduced airway neutrophil recruitment (P = 0.002) and reduced lung pathology (P = 0.031). Calves receiving SCFP shed less virus than control calves (P = 0.028) and tended toward lower viral loads in the lungs (P = 0.051). Immune cells from the peripheral blood of SCFP treated calves produced increased (P < 0.05) quantities of IL-6 and TNFα in response to toll-like receptor stimulation; while cells from the BAL secreted less (P < 0.05) proinflammatory cytokines in response to the same stimuli. Results from this study suggest that supplementing with SCFP modulates both systemic and mucosal immune responses and may improve the outcome of an acute respiratory viral infection in preweaned dairy calves.

Keywords: Saccharomyces cerevisiae fermentation products, bovine respiratory disease, innate immunity.