Reproductive Performance of Beef Heifers Supplemented with Corn Gluten Feed and Rumen-Protected Fat before Breeding

A rumen-protected fat (Megalac) and corn gluten feed supplement (RPCG) was fed to heifers to determine reproductive effects. Angus (n = 24) and Polled Hereford (n = 17) heifers (initial BW 376.9 ± 29.9; kg average age 14 mo) were randomly assigned 60 d before breeding began to the following treatments: control (n = 20; no supplementation), or RPCG supplement (n = 21; 8% Megalac, 92% corn gluten feed; fed 5 d/wk at 3.45 kg/ heifer daily). Breeding began April 14 using AI (d 1 to 44), and bulls (d 45 to 71). Heifer BW (kg) and ultrasound subcutaneous fat (cm) for control and RPCG, respectively, were as follows: February 11 = 376 and 373, 2.23 and 2.15, SE 6.4 and 0.11; April 11 = 431 and 434, 2.20 and 2.36, SE 6.4 and 0.11; June 18 = 444 and 446, 2.09 and 2.22, SE 3.1 and 0.11; (control vs. RPCG: P > 0.10 for BW and ultrasound subcutaneous fat). Serum cholesterol (mg/dL), high-density lipoprotein (HDL; mg/dL), leptin (ng/mL), on d 60 for control were 139.6, 100.9, and 8.38, respectively, and for RPCG were 162.9, 122.2, and 10.70 (control vs RPCG for cholesterol and HDL, P < 0.01; for leptin, P < 0.05). Interactions of treatment sampling date for cholesterol and HDL (P < 0.01) and for leptin (P < 0.05) showed each lipid increasing with time on RPCG compared with control. Feeding RPCG to heifers before breeding increased serum lipids by d 60, resulting in a trend for increased pregnancy rates in these heifers (RPCG vs control, 79.2 vs 56.2%; P > 0.10).