Total plasma concentrations of cortisol were reduced by 19–25% (p < 0.05), but serum concentrations of insulin, growth hormone, and IGF-I were increased (p < 0.05) by 22–29%, 24–31%, and 26–31% in IUGR piglets receiving the oral administration of 0.4–0.8 g Arg/kg BW/day, respectively, compared with the control group. The gene discussed is GH1; the disease is fetal growth restriction.