Animal Science, Department of


Date of this Version

January 2000


Published in Nebraska Beef Cattle Report 2000, published by Agricultural Research Division, University of Nebraska Cooperative Extension, and Institute of Agriculture and Natural Resources, University of Nebraska–Lincoln.


A two-year study was conducted on 240 yearling heifers to refine the MGA/ PGF synchronization program by using a 19-day PGF injection. All heifers were fed MGA for 14 days and received PGF injection on either Day 17 or Day 19 after the MGA period. Heifers were heat detected and bred by AI using semen from one sire. The Day 19 PGF injection caused a higher (16%) percentage of heifers to cycle by 72 hours after injection, a higher (6%) percentage of heifers to cycle during the 5-day breeding period, and higher pregnancy rates in 5 days (8%) and in 50 days (5%) than heifers given PGF on Day 17. Similar results were found on a cooperating ranch using 1400 heifers.