Soy isoflavones are naturally occurring compounds with a wide variety of biological activities, including estrogenic, anti-inflammatory and anti-oxidative properties that could be beneficial in disease-challenged pigs. Previous work has shown that isoflavones reduce viral replication and infectivity, decrease expression of pro-oxidative cellular signaling pathways and influence the production of both pro- and anti-inflammatory cytokines utilized by the immune system. While most of these biological actions were demonstrated in the laboratory, not the field, experiments performed by Dr. Ryan Dilger’s laboratory at the University of Illinois at Urbana-Champaign demonstrated that dietary soy isoflavones may provide health benefits in growing pigs facing a respiratory disease challenge.
Researchers investigated how isoflavones influenced the long-term response and recovery from PRRSV in growing/finishing pigs, with pigs observed from weaning to market weight. Pigs receiving dietary isoflavones demonstrated inconsistent differences in growth performance but increased neutrophil cell counts, increased relative proportions of memory T-cells and decreased time to full PRRSV antigen clearance from oral fluids, again indicating a more robust immune response. The most notable finding, however, was that PRRSV-infected pigs consuming isoflavones exhibited approximately 50% less mortality than infected pigs not receiving isoflavones even though both diets delivered exactly the same concentrations of amino acids.
In conclusion, while it is clear that dietary isoflavones from soy improve outcomes for pigs facing health challenges, more information is needed to determine the specific biological mechanism(s) of action and how farmers can use dietary isoflavones in the diets of growing pigs to increase their health and productivity.