Fetal and postnatal growth are mediated by insulin-like growth factors (IGFs) and their binding proteins (IGFBPs). Maternal nutrient intake during gestation can program the postnatal IGF-axis. This may have significant economic implications for beef cattle production. We investigated the effect of high (H=240%) and low (L=70%) levels of recommended daily crude protein (CP) intake for heifers during the first and second trimesters of gestation in a two-by-two factorial design on progeny (n=68) plasma IGF-I, IGF-II, total IGFBP (tIGFBP), postnatal growth and carcass traits. Calves were heavier at birth following high CP diets during the second trimester (P=0.03) and this persisted to 29d. Plasma IGF-I concentrations of males were greater for HL compared to LL (P0.04) from 29 to 657d, and for LH compared to LL from 29 until 379d (P=0.02). Exposure to low CP diets during the first trimester resulted in heavier males from 191d onwards (P=0.04) but a tendency for lighter females from 552d onwards (P=0.07) that had lighter carcass weights (P=0.04). Longissimus dorsi cross-sectional area of all carcasses was greater following exposure to low CP diets during the second trimester (P=0.04). Heifer nutrient intake during the first and second trimesters causes persistent and sex-specific programming of progeny plasma IGF-I, postnatal liveweight and carcass weight. Refining heifer nutritional programs during early gestation may optimize production objectives in progeny. ; G.C. Micke, T.M. Sullivan, K.L. Gatford, J.A. Owens and V.E.A. Perry