Beef cattle production: Understanding the effect of heifer development system, late gestation protein supplementation, and ovarian steroidogenic environment on productivity, reproduction, and longevity

A 3-yr study was conducted to determine the effect of heifer development system on ADG, reproductive performance, and subsequent feed efficiency as a pregnant heifer. Crossbred Angus heifers (n= 299) were assigned by initial BW to be developed grazing corn residue (CR) or in a drylot (DL). Corn residue heifers grazed native pasture 33 d prior to grazing CR 73 d. Corn residue heifers were then placed on dormant forage pastures 67 d and then combined with DL heifers for approximately 39 d for estrus synchronization and AI. Heifers assigned to DL grazed dormant forage for 98 d and then placed in a DL for 114 d. Prebreeding BW was greater (P = 0.01) for DL heifers compared with CR heifers (349 vs. 314 ± 9 kg). At pregnancy diagnosis BW remained greater (P = 0.05) for DL compared with CR heifers (422 vs. 403 ± 9 kg). Drylot heifers had greater (P = 0.01) overall ADG during development compared with CR heifers. Corn residue-developed heifers tended (P = 0.11) to have increased AI conception rates compared with DL heifers (74 vs. 65 ± 8). However, there was no difference (P ≥ 0.32) in percent cycling (42 vs. 52 ± 15%) prior to the breeding season or final pregnancy rates (95 vs. 92 ± 2%) for CR and DL heifers, respectively. Gestation length, calving date, and calf birth BW were similar (P ≥ 0.37) between development systems. At the beginning of the second winter, a subset of AI pregnant heifers (n = 114) were stratified by BW and