52 Alterations of fecal microbiome characteristics by dietary soy isoflavone ingestion in growing pigs infected with porcine reproductive and respiratory syndrome virus

Abstract

Abstract Porcine reproductive and respiratory syndrome virus (PRRSV) is an economically-important disease and ingestion of soy isoflavones (ISF) may benefit PRRSV-infected pigs due to demonstrated anti-inflammatory and anti-viral properties. The objective of this study was to quantify long-term effects of ISF consumption on fecal microbiome characteristics under disease challenge. In total, 96 weaned barrows were group-housed in a BSL-2 containment facility and allotted to 1 of 3 experimental treatments that were maintained throughout the wean-to-finish study: non-infected pigs receiving an ISF-devoid control diet (NC, n=24), and infected pigs receiving either the control diet (PC, n=36) or that supplemented with total ISF in excess of 1,600 mg/kg (ISF, n=36) (Table 1). Following a 7-day adaptation, pigs were inoculated intranasally with either a sham-control (PBS) or live PRRSV (1×105 TCID50/mL, strain NADC20). Fecal samples were collected from 48 individual pigs at pre-infection (-2 days post-inoculation, DPI), peak-infection (10 DPI), and post-infection (144 DPI) time-points and extracted DNA was used for 16S bacterial rRNA sequencing. Differences in bacterial communities among diet groups were evaluated using UniFrac distance matrices (weighted and unweighted) in QIIME. All other data were analyzed by one-way ANOVA performed on transformed data using R. Across all time-points, only minimal differences were observed due to ISF alone. At 10 DPI, PRRSV infection reduced Prevotella 9 genera abundance from approximately 20% to less than 10%, but the specific function of this variety in pigs is unclear. The most notable finding was decreased relative abundance of Actinobacteria at 144 DPI between non-infected and infected treatments (P < 0.05), which is consistent with various dysbioses observed in other disease models. Our findings indicate that differences present were mainly due to PRRSV infection and not strongly influenced by ISF ingestion, which implies previously observed performance benefits conferred by dietary ISF are not likely due to changes in microbiome composition.