Twelve replications of four littermate pigs from a herd without porcine reproductive and respiratory syndrome (PRRS) were weaned at 10 days and penned individually in isolation rooms. The pigs were randomly allotted within litter to four dietary soy genistein treatments (0, 200, 400 & 800 ppm) to determine the effect of genistein (a soy isoflavone) on pig growth and virus replication during a viral challenge. The pigs were challenged at 29 days of age with a known level and strain of the virus. Pig performance, feed intakes and serum concentrations of the PRRS virus were monitored. Based on this study, it would appear that soy genistein (200 ppm) is an orally active immune modulator that can reduce virus replication and improve growth in virally challenged pigs. The researchers concluded that the level of soy isoflavones may improve the biological response of animals to pathogens and/or vaccines.

Griener, L.L., T.S. Stahly and T.J. Stabel. 2001. The effect of soy genitstein on pig growth and viral replication during a viral challenge. J. Animal Sci.