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The objective of this research was to evaluate the effects of two implant programs and differing days-on-feed (DOF) on net returns of beef feedlot heifers using sensitivity analyses of key economic factors. Crossbred beef heifers [ n  = 10,583; initial weight 315 kg (± 20.1 SD)] were enrolled across three trials (one Kansas, two Texas feedlot trials). Heifers were blocked by arrival and randomly allocated to one of six pens, resulting in a total of 144 pens and 24 blocks. Pen was randomly assigned to treatment as a 2 × 3 factorial. Implant programs were: IH + 200-Revalor-IH at initial processing, and a terminal implant after approximately 90 DOF (Revalor-200), or, XH-a single implant at initial processing (Revalor-XH). The DOF treatments were: heifers fed to a standard baseline endpoint (BASE) or heifers fed for an additional + 21 or + 42 d beyond BASE. Pen-level partial budgets were used for economic sensitivity analyses, which varied price points of single pricing components with all other components fixed. Variable components were live-fed cattle prices, base carcass prices (i.e., dressed), Choice-Select spread (CS-spread), and feed and yardage prices (FYP). For each, a Low, Mid-Low, Middle, Mid-High, and High price was chosen. Linear mixed models were fit for statistical analyses (α = 0.05). There were no significant two-way interactions ( P -values ≥ 0.14). Regardless of the variable component evaluated, XH heifers had poorer net returns than IH + 200 at all prices ( P  ≤ 0.04). Selling live, the + 21 and (or) + 42 heifers had lower net returns than BASE at every fed cattle price point ( P  < 0.01). Selling dressed, the + 21 and (or) + 42 heifers had lower returns than BASE at Low, Mid-Low, and Middle fed cattle base prices ( P  < 0.01); there were no significant DOF differences at Mid-High, or High prices ( P  ≥ 0.24). Net returns were lower for + 42 than BASE at all CS-spreads ( P  ≤ 0.03), while BASE and + 21 did not differ significantly. Longer DOF had lower net returns than BASE when selling live at every FYP ( P  < 0.01) except at the Low price ( P  = 0.14). Selling dressed, there was no significant effect of DOF at Low or Mid-Low FYP ( P  ≥ 0.11); conversely, extended DOF had lower net returns than BASE at Middle, Mid-High, and High FYP ( P  < 0.01). Overall, there was minimal economic evidence to support extending feedlot heifer DOF beyond the BASE endpoint, and when feeding longer, larger reductions in return were observed when marketing live as opposed to dressed., Competing Interests: Merck Animal Health employs JH and MS; their contributions were intellectual as they did not partake in data collection or analyses. No competitive interest was present due to non-use or evaluation of competing products. There are no conflicts of interest to disclose., (© The Author(s) 2024. Published by Oxford University Press on behalf of the American Society of Animal Science.)

Research objectives were to evaluate effects of two implant programs for beef heifers fed three different durations (days-on-feed; DOF) on carcass weight and composition (primary outcomes) and feedlot performance (secondary outcomes) at commercial feedlots. Data from a randomized trial in Kansas were analyzed separately and also pooled with data from two previously published trials conducted in Texas. Heifers were randomly allocated to pens within a block, and pens were randomized to treatments in a 2 × 3 factorial randomized complete block design. Implant programs were IH + 200 - an initial Revalor-IH implant [80 mg trenbolone acetate (TBA) and 8 mg estradiol (E 2 )] and a re-implant after a mean of 98-d (± 10.8 SD) with Revalor-200 (200 mg TBA and 20 mg E 2 ), or XH - Revalor-XH, a single extended-release implant (200 mg TBA and 20 mg E 2 ). Heifers were fed to a baseline endpoint (BASE; pooled mean 166-d ± 11.9 SD), +21, or +42 additional DOF. A total of 10,583 crossbred heifers with mean initial body weight (BW) 315 kg (± 20.1 SD) were enrolled in 144 pens in 24 blocks (treatment replications) across the three trials. General and generalized linear mixed models accounting for clustering of trials, blocks, and pens were used to test for effects of treatments, with significance set at α = 0.05. The only implant program × DOF interaction in pooled analyses was for dry matter intake (DMI; P < 0.01); IH + 200 heifers had lower mean DMI than XH when fed +42 DOF. Gain:feed was higher for IH + 200 compared to XH with dead and removed animals excluded ( P < 0.01) or included ( P = 0.03). For IH + 200, hot carcass weight (HCW) increased ( P < 0.01), USDA Yield Grade (YG) distributions shifted towards lower numerical categories ( P < 0.01), and Prime carcasses decreased while Select increased compared to XH ( P < 0.01). For each incremental increase in DOF, final BW ( P < 0.01) and HCW increased ( P < 0.01), while daily gain ( P < 0.01) and gain:feed ( P < 0.01) decreased. Categories of YG were affected by DOF ( P < 0.01); there were fewer YG 1 and 2 and more YG 4 and 5 carcasses for +42 compared to BASE and +21. USDA Quality Grade (QG) distributions differed by DOF ( P < 0.01); each incremental increase in DOF resulted in more Prime and fewer Select carcasses. Without meaningful interactions, tested implant programs likely have a consistent effect when heifers are fed to similar DOF, while changes in HCW, QG, and YG may influence marketing decisions when extending DOF., (© The Author(s) 2022. Published by Oxford University Press on behalf of the American Society of Animal Science.)