Beef heifers (n = 1524) from two operations in central Nebraska were randomly assigned to one of two treatments [0 or 5 μg GnRH at prostaglandin F2α (PGF) administration 72 hrs before insemination]. Both locations utilized MGA-PG fixed-time AI (TAI) estrus synchronization protocol. The first location (L1, n = 1076, 382 ± 3 kg) processed heifers 72 hours prior to insemination and every third heifer was assigned to receive an injection of GnRH (5 ug) (TRT) and an injection of PGF. The remaining heifers received PGF and 0 μg GnRH. At insemination all heifers received 100 ug GnRH. Heifers were then observed for estrus behavior from 10–21 days post TAI and re-inseminated if estrus was detected. Heifers pregnant from the second breeding were added to final pregnancy rate. The second location (L2) utilized estrus detection patches and performed only TAI (n = 448, 363 ± 7 kg) following MGA-PG synchronization protocol outlined above without the estrus observation period. Treatment did not significantly (P > 0.20) improve TAI pregnancy rates [L1 TAI 56.3% (TRT) vs 57.3%; L1 AI Total 78.3% (TRT) vs 73.9%; L2 TAI 58.5% (TRT) vs 52.5%] among the two herds. The administration of 5 μg GnRH at PGF tended to increase (P = 0.12, 74% vs 63%) pregnancy rates for those inseminated during the follow up heat detection period at L1. The treatment did not (P > 0.20) improve pregnancy for the time-AI heifers. In addition, TAI pregnancy rates were similar (P > 0.20) at L2. There were greater (P < 0.20) effect of pen on pregnancy rate.

A 3-yr study evaluated the economic differences between a March and May calving production system of crossbred beef cows and their offspring from the Gudmundsen Sandhills Laboratory, Whitman, NE. Both herds were treated as a common when not in treatment period. Adjusted calf weaning BW was higher (P) for March Calves (226.4 ± 1.1 kg vs 193.4 ± 2 kg). Pregnancy rates (89% vs 91%) were similar through both systems. The stochastic economic model used for the analysis was based on 9 yr of USDA AMS data. The model accounts for most assumptions within each system, including all labor, cull and replacement cow costs and feed costs. This analysis was on the total calf costs, total pair feed costs and average market net return at weaning. March systems wintered on hay had a positive net return 2 out of the 9 yr (Average of -$88.76/calf) and on cornstalks 8 out of 9 years in Dawson County, NE (Average of $62.75/calf). March systems on winter range feed 0.41 kg DM/(cow • d) of supplement had a positive net return 4 out of the 9 yrs (Average of $25.23/calf). The May system, no matter the treatments of range or meadow and with or without supplement, had a positive net return 2 out of the 9 years (Average of $-65.77 and $-83.90/calf). Within this analysis, even with the input costs being higher for March, the net return was still greater in a March vs May system. Further analysis will be done on different trts within each system.

No abstract

No abstract