LAUSR

Objectives were to determine the influence of a vitamin and mineral supplement (VTM), an energy supplement (NRG), and day post-artificial insemination (DPAI) on concentrations of glucose and non-esterified fatty acids (NEFA) in beef heifers. Cross-bred heifers (n = 72; initial weight = 351.2 kg) were assigned to 4 treatments arranged as a 2 × 2 factorial with main factors of VTM and NRG supplement. Treatments were: 1) control (no VTM or NRG), 2) VTM (initiated 71 to 106 before breeding) only, 3) NRG (initiated at breeding) only, and 4) VTM and NRG. Heifers were synchronized then bred via artificial insemination on d 0. Blood was drawn on d -9, 14, 28, and 42 from all heifers and on d 56, 70, and 84 from pregnant heifers (n = 31). Plasma samples were analyzed for concentrations of glucose and NEFA. Data were analyzed using the MIXED procedure in SAS. There were no interactions between VTM, NRG, or DPAI (P > 0.05). In addition, pregnancy status did not influence concentrations of glucose or NEFA (P > 0.05). There were no effects (P > 0.35) of VTM on glucose or NEFA concentrations. Energy supplementation increased (P = 0.012) glucose and decreased (P = 0.013) NEFA concentrations. Glucose concentrations were greatest at d -9, decreased through d 42, and then, on d 70 and 84 increased to levels similar to d -9 (81.9, 76.1, 73.6, 73.7, 74.3, 76.2, and 78.4 ± 2.97 for d -9, 14, 28, 42, 56, 70, and 84, respectively). Concentrations of NEFA were greater (P < 0.01) at d -9 compared with 14, 28, 42, 56, and 70, and concentrations on d 84 were greater (P < 0.01) than all other days. In conclusion, glucose and NEFA were affected by NRG and DPAI, but not VTM.