PSIII-12 - The Effect of Maternal Dietary Isoflavone Supplementation and Infection with Porcine Reproductive and Respiratory Syndrome Virus on the Growth Performance of Offspring

The objective of this experiment was to evaluate the effects of maternal infection with porcine reproductive and respiratory syndrome virus (PRRSV) on piglet prenatal development and pre-weaning growth, and the potential for isoflavone supplementation to alleviate these effects. First parity gilts (n = 24) at gestational day (GD) 65 were allotted to one of three treatments: uninfected and fed a diet devoid of isoflavones (CON), infected with PRRSV and fed the control diet (POS), or infected with PRRSV and fed a diet supplemented with 1,500 ppm soy isoflavones (ISF). Gilts were inoculated intranasally with saline or 2.5×10⁴ TCID₅₀/mL of suspended live PRRSV (NADC₂₀ strain) on GD 70. To determine the effects of PRRSV infection in sows, feed intake (GD 70-114) and rectal temperatures (GD 70-91) were recorded daily, while serum TNF-α concentrations were measured weekly. After farrowing (GD 114 ± 2), two piglets closest to the average litter weight were culled either at birth or weaning (21 d of age) to determine body, muscle, and organ weights of offspring pigs. Hematoxylin and eosin staining was performed on left semitendinosus muscles for determination of muscle cell number and size at each time-point. At birth, whole body, muscle, and organ weights were not different (P > 0.22) between groups except that relative liver weight was increased (P < 0.05) in POS compared with CON piglets. At weaning, ISF reduced (P ≤ 0.05) whole body and muscle weights, but greater (P < 0.05) kidney weight compared with CON, and greater (P < 0.05) relative liver weight compared with CON or POS. However, muscle fiber number and size were not different (P > 0.39) between groups at either time-point. These results suggest maternal PRRSV infection altered offspring organ growth, but dietary ISF did not alleviate the detrimental effects of PRRSV infection in sows or offspring.