July 06, 2020

Interpretive Summary: Feeding soy isoflavones to growing pigs with PRRSV

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

By: Anne Wallace

Soy isoflavones (ISF) are naturally occurring antioxidants with antiviral and anti-inflammatory properties. Feeding soy ISF to pigs mitigates the negative impacts of porcine reproductive and respiratory syndrome virus (PRRSV), an economically devastating disease.

Boosting swine immunity is necessary to prevent production losses in swine farms due to PRRSV infection. However, the mechanism by which soy ISF improves performance during PRRSV infection is not well understood. It is possible that soy ISF may improve the immune function of growing pigs by alterations to the gut microbiome. In this Journal of Animal Science study (June 2020), researchers explored a fecal microbiome hypothesis to potentially explain why soy ISF feeding benefits pigs infected with PRRSV.

Pigs were infected with PRRSV and fed either a diet containing soy ISF or a diet without soy ISF. An additional group serving as the negative control was not infected with PRRSV and fed a diet without soy ISF. Fecal samples were collected at three different time points (2 days before infection, and 10 and 144 days after infection). Bacteria were identified by 16S rRNA sequencing. Results indicated that at 144 days there was a significant difference in the relative abundance of the phylum Actinobacteria in infected versus non-infected pigs. The authors note this finding suggests gut dysbiosis. There were no notable changes in the fecal microbiomes of infected pigs based on the feeding of soy ISF.

Overall, the results of this study suggest that the mechanism by which soy ISF improves the performance of PRRSV-infected pigs is likely not via their fecal microbiome. Other potential ways that soy ISF feeding might improve immunity, for example, by down-regulation of inflammatory cytokines, should be investigated in future studies.