Cattle, carcass, economic, and estimated emission impacts of feeding finishing steers lubabegron or ractopamine hydrochloride

Lubabegron (Experior; Elanco, Greenfield, IN, USA) is the first U.S. Food and Drug Administration approved feed additive for reducing gas emissions from feedlot animals or their waste; it does not have live or carcass performance claims. Our primary objective was to determine the effect of lubabegron on feedlot performance and carcass traits in finishing beef steers compared to ractopamine hydrochloride (Optaflexx; Elanco, Greenfield, IN, USA). A commercial feedlot trial using cross-bred beef steers (n = 2,117; 373 ± 15 kg initial body weight [BW]) was completed with a randomized complete block design. Treatments consisted of two feed additives: (1) OPT targeted to deliver 300 mg/animal/d of ractopamine hydrochloride for 28 ± 7 d out from harvest and (2) EXP targeted to deliver 36 mg/animal/d of lubabegron 56 ± 7 d out from harvest and a 4-d preslaughter withdrawal period. Twenty 70 to 142 hd pens with 10 pens per treatment were used. Cattle were weighed at arrival processing and at harvest and fed for an average of 167 d. Data were used to calculate production metrics, partial budgets, and estimated greenhouse gas emissions using published methods, and were analyzed using linear mixed models with pen as the experimental unit and block as a random intercept. A statistical significance threshold of α = 0.05 was determined a priori. There was no evidence for statistically significant differences between treatments for initial BW (P = 0.70), health-related outcomes (P values ≥ 0.43), or mobility scores (P = 0.09). Cattle-fed EXP had increased final BW, ADG, G:F, and decreased dry matter intake (P values ≤ 0.01) compared to OPT. Carcasses were 11 ± 1.76 kg (hot carcass weight) heavier in EXP group (P < 0.01), and differed between treatments for both yield grades (YG) and quality grades distributions (P values ≤ 0.01). Cattle-fed EXP had a shift toward more YG 1 and 2, select and sub-select carcasses compared to OPT, which had as shift toward more YG 3, 4, 5, prime and choice carcasses. With increased beef production and efficiency compared to OPT, the estimated CO2 equivalent emissions from production were reduced by 6.2% per unit of carcass weight for EXP (P ≤ 0.01). Estimated net returns/animal shipped were $56.61 ± 9.37 more for EXP than OPT (P ≤ 0.01). In conclusion, when cattle were fed for the same total number of days, feeding EXP compared to OPT increased net returns, feedlot performance, and efficiency, but resulted in carcass yield and quality characteristics that may impact marketing programs.

Net return distributions when metaphylaxis is used to control bovine respiratory disease in high health-risk cattle

This study’s objective was to estimate net returns and return risk for antimicrobial metaphylaxis options to manage bovine respiratory disease (BRD) in high health-risk feedlot cattle. The effectiveness of antimicrobials for metaphylaxis varies by cattle population. How differing antimicrobial effectiveness translates to net return profitability for heterogeneous cattle populations is less understood. Net returns and return risk were assessed using a net return simulation model adapted to allow for heterogeneity in high health-risk cattle placement characteristics and antimicrobial choice to control BRD. The net return model incorporated how antimicrobials modify BRD health and performance outcomes. Health and performance outcomes were calibrated from published literature and proprietary feedlot data. Proprietary data came from 10 Midwestern feedlots representing nearly 6 million animals and 50,000 cohorts. Twelve placement-by-metaphylaxis decision combinations were assessed: high health-risk steer placement demographics were 600 or 800 lb steers placed in Winter (Oct–Mar) or Summer (Apr–Sept) managed with one of three different health programs: “no metaphylaxis,” “Upper Tier” antimicrobial, or “Lower Tier” antimicrobial. Net return distributions were compared between “no metaphylaxis” and a specific antimicrobial tier within specific cattle populations. We found the expected incremental net return of administering an “Upper Tier” (“Lower Tier”) antimicrobial for metaphylaxis compared to “no metaphylaxis” for high health-risk steers was $122.55 per head ($65.72) for 600 lb and $148.65 per head ($79.65) for 800 lb winter placements. The incremental expected net return and risk mitigated by metaphylaxis varied by placement weight, season, and antimicrobial choice. The probability net returns would decline by at least $50 per head was significantly reduced (from approximately 4% to 40%) when any antimicrobial was used on high health-risk steers. Both tiers of antimicrobials used for metaphylaxis increased expected net returns and decreased net return variability relative to no metaphylaxis. Thus, feedlots were more certain and realize a greater profit on high health-risk pens of steers when metaphylaxis was used. This occurred because the reduction in cattle health and performance outcomes using any antimicrobial was sufficiently large to cover added initial and subsequent antimicrobial costs. Results aid in assessing metaphylaxis strategies in high health-risk cattle.

Positive and normative modeling for Palmer amaranth control and herbicide resistance management

BACKGROUND

Dynamic optimization models are normative; they solve for what growers 'ought to do' to maximize some objective, such as long-run profits. While valuable for research, such models are difficult to solve computationally, limiting their applicability to grower resistance management education. While discussing properties of normative models in general, this study presents results of a specific positive model of herbicide resistance management, applied to Palmer amaranth control on a representative cotton farm. This positive model compares a proactive resistance management strategy to a reactive strategy with lower short-run costs, but greater risk of herbicide resistance developing.

RESULTS

The proactive strategy can pay for itself within 1-4 years, with a yield advantage of 4% or less if the yield advantage begins within 1-2 years of adoption. Whether the proactive strategy is preferable is sensitive to resistance onset and yield losses, but less sensitive to cotton prices or baseline yields. Industry rebates to encourage residual herbicide use (to delay resistance to post-emergence treatments) may be too small to alter grower behavior or they may be paid to growers who would have used residuals anyway. Rebates change grower behavior over a relatively narrow range of model parameters. The size of rebates needed to induce a grower to adopt the proactive strategy declines significantly if growers extend their planning horizon from 1 year to 3-4 years.

CONCLUSIONS

Whether proactive resistance management is more profitable than a reactive strategy is more sensitive to biological parameters than economic ones. Simulation results suggest growers with longer time horizons (perhaps younger ones) would be more responsive to rebate programs. More empirical work is needed to determine how much rebates increase residual use above what would occur without them. © 2017 Society of Chemical Industry.