LAUSR

Objectives were to evaluate effects of early gestation energy supplementation on heifer body weight (BW), IGF-1 concentrations, and calf characteristics. One-hundred Angus-based heifers (initial BW = 371.1 ± 3.9 kg) were estrous synchronized, bred to female-sexed semen, then randomly assigned to either a basal diet to achieve 0.20 kg/d (CON, n = 50) or a basal diet plus supplemental energy to achieve 0.75 kg/d gain (SUPP, n = 50) for 84 d. The CON diet consisted of 37% corn silage, 53% prairie hay, and 10% distillers dried grain with solubles (DDGS). The SUPP diet was 29% corn silage, 41% prairie hay, 5% DDGS, and 25% corn/PurinaAccuration Range Supplement 33 blend. Heifers were individually fed via Insentec feeders (Insentec Marknesse, The Netherlands), with bi-weekly feed delivery adjustments to achieve targeted gains. After d 84, heifers were managed as a single group on pasture, then in a dry lot until parturition. A total of 46 heifers gestated female pregnancies to term (n = 23 CON and n = 23 SUPP). Body weights and blood samples were collected on d 0, 42, 84, 162, 234, 262, and at parturition. By design, SUPP heifers were 55.4 kg heavier (P < 0.0001) than CON at d 84. Weight divergence remained throughout gestation, with SUPP heifers being 41.5 kg heavier at parturition (P < 0.0001). For SUPP, IGF-1 concentrations were greater throughout gestation (P = 0.003). Fetal size, as measured by ultrasound, was not affected by treatment at d 42 (P = 0.50), 63 (P = 0.35), or 84 (P = 0.20); however, calves from SUPP dams were 2.1 kg heavier (P = 0.03) and had larger chest circumference (P = 0.05) at birth compared with CON. Early gestation nutrition impacted heifer BW and IGF-1 concentrations throughout gestation, and clearly impacted in utero fetal growth.