76 Awardee Talk: Maternal Immune Activation Impacts Offspring Immune Function but not Muscle

Abstract

Abstract Gestational health challenges may influence growth performance and immunity of offspring pigs during postnatal life. In particular, porcine reproductive and respiratory syndrome virus (PRRSV) is endemic in the U.S. herd, but its effects on surviving piglets are largely unknown. Further, dietary supplementation with soy isoflavones lessened the severity of PRRSV infections in weaning and growing pigs. Therefore, the goals of this study were to determine the impact of maternal PRRSV infection on offspring muscle and immune development and the potential of isoflavones to mitigate those effects. Thirteen first parity gilts were randomly allotted to 1 of 3 treatments: fed a diet devoid of isoflavones and not infected (CON), fed the control diet and infected with PRRSV (POS), and fed the control diet supplemented with 1,500-ppm soy isoflavones and infected with PRRSV (ISF). Isoflavone supplementation reduced (P = 0.04) viral load in dams 21d after infection, but did not alter (P > 0.05) feed disappearance and rectal temperature. Piglet mortality was increased (P = 0.04) by PRRSV infection in dams, and surviving piglets were infected with PRRSV throughout the study. Interestingly, muscle and organ weights were not different (P > 0.05) among treatments at postnatal d (PND) 3 with the exception of relative liver weight which was increased (P = 0.04) in POS compared with CON, with ISF being intermediate. Infected litters were lighter (P = 0.02) at PND 21, likely due to postnatal infection. Interestingly, at PND 21 relative liver weight was increased (P < 0.01) in ISF compared with CON and POS. Muscle fiber number and size did not differ between treatments (P ≥ 0.39). Piglets born to infected dams had slower responses during innate immune stimulation (P < 0.01) and also had shifts in T cell populations compared with CON pigs (P ≤ 0.02), indicating an inadequate vaccine response. Overall, maternal infection altered offspring immune responses but not muscle fiber development. Isoflavone supplementation did not mitigate these effects.