520 Late-Breaking: Effect of Technology on Environmental Emissions from Four Representative U.S. Feedlots and the Beef Production System

Our objective was to evaluate effects of technological management strategies on environmental impacts and net returns of feedlot operations in the United States. Feedlot operations were simulated with the Integrated Farm System Model (IFSM 4.6; USDA-ARS, University Park, PA) to quantify baseline environmental impacts of feedlot production and full US beef cattle production systems. Strategies simulated included: ionophore, implant, ractopamine hydrochloride, combined management (ionophore, implant, and ractopamine hydrochloride; I+I+R), lubabegron, reduced mortality rate, and improved fiber digestion. Days on feed were adjusted whenever necessary and according to production practices typical of commercial feedlots. Subsequently, annual number of cattle finished by the operation was adjusted according to days on feed to maintain consistent one-time capacities. Mitigation strategies were individually modeled and simulated in IFSM for each feedlot operation to calculate intensities (expressed per kg gain) for greenhouse gas (GHG) emissions, fossil energy use, blue water consumption, and reactive nitrogen loss. Additionally, net returns to management were estimated for each feedlot operation. Feedlots were then integrated with simulations of cow-calf, stocker, and backgrounding operations to estimate environmental intensities (expressed per kg carcass weight) for the full beef cattle production system. Carbon emission intensity was reduced most using the I+I+R strategy (10%), followed by implant (6%) and ionophore (5%) strategies alone. Similarly, energy use intensity was reduced the greatest by I+I+R (9%), ionophore (5%), and implants (4%). Reductions in water use intensity were also greatest using I+I+R (9%). Net returns increased for all strategies compared to baseline net return with the greatest improvements observed for I+I+R ($114/finished animal) and implants ($66/animal). Consistent results were observed for all strategies simulated across all four environmental intensities when quantified for the full cattle production system. Implementing I+I+R (7%), ractopamine hydrochloride (4%), and lubabegron (4%) in feedlots resulted in the greatest reductions in environmental emissions.

Effect of trenbolone acetate, melengestrol acetate, and ractopamine hydrochloride on the growth performance of beef cattle

The effect of trenbolone acetate+estradiol implants (TBA), melengestrol acetate (MGA), and ractopamine hydrochloride+TBA (RAC+TBA) on growth performance and carcass characteristics in beef cattle (n=680; 279±10.1 kg) fed barley grain/corn silage was examined in a 4-yr study (4 pens/treatment/yr; 262 ±8 d feeding period). In the first 2 yrs, treatments were: 1) control heifers (H-CON; no growth promoters (GP), 2) TBA implanted heifers (H-TBA), 3) MGA heifers (H-MGA), 4) control steers (S-CON; no GP), and 5) TBA implanted steers (S-TBA). A sixth treatment 6) RAC+TBA steers (RAC+TBA) was included in yrs 3 and 4. Overall DMI of heifers was increased (P<0.001) by TBA, but not MGA. Compared to H-CONs, H-TBA had greater ADG (P <0.001), G:F (P < 0.001), and carcass weight (P < 0.001), whereas S-TBA had increased ADG (P < 0.001), G:F (P< 0.001), and carcass weight (P< 0.001) compared to S-CON. Compared to H-CON, H-MGA had increased (P< 0.01) ADG, G:F and carcass weight. The RAC+TBA had increased (P< 0.01) ADG and carcass weight (3.2%), but not G:F or DMI compared to S-TBA. This 4 yr study showed a consistent positive impact of growth-enhancing technologies on the performance of Canadian feedlot cattle.

Effect of ractopamine hydrochloride on environmental gas emissions, growth performance, and carcass characteristics in feedlot steers

With a growing global population and increased environmental concerns around animal agriculture, it is essential to humanely maximize animal performance and reduce environmental emissions. The present study aims to determine the efficacy of feeding ractopamine hydrochloride (RAC), an orally active, β1–adrenergic agonist (β1AA), to feedlot steers in the last 42 d of finishing to reduce ammonia (NH3) emissions and improve animal performance. A randomized complete block design was used to allocate 112 Angus and crossbred Angus steers (Initial BW = 566.0 ± 10.4 kg) to 8 cattle pen enclosures. Pens (n = 4/treatment, 14 steers/pen, 56 steers/treatment) were randomly assigned to 1 of 2 treatments: 1) CON; finishing ration containing no RAC, 2) RAC; finishing ration containing 27.3 g/907 kg dry matter (DM) basis RAC. Steers were weighed on d -1 and 0 before treatment and d 14, 28, and 42 during treatment. Treatment rations were mixed and delivered daily by masked personnel. Measured emissions included NH3, nitrous oxide (N2O), methane (CH4), hydrogen sulfide (H2S), and carbon dioxide (CO2). The primary response variables assessed were emissions standardized by live weight (LW) and hot carcass weight (HCW). Steers were harvested on d 43 and carcass data was collected on d 43 and 44. Steers fed RAC reduced NH3 emissions by 17.21% from d 0 to 28 (P = 0.032) and tended to reduce NH3 from d 0 to 42 by 11.07% (P = 0.070) vs. CON. When standardized for LW, NH3 was reduced by 23.88% from d 0 to 14 (P = 0.018), 17.80% from d 0 to 28 (P = 0.006), and 12.50% for d 0 to 42 (P = 0.027) in steers fed RAC vs. CON. Steers fed RAC had 14.05% (P = 0.013) lower cumulative NH3 emissions when standardized by HCW vs. CON. Feeding RAC to Steers reduced H2S by 29.49% from d 0 to 14 (P = 0.009) and tended to reduce H2S over d 0 to 28 by 11.14% (P = 0.086) vs. CON. When H2S emissions were standardized for LW, RAC fed steers had a 28.81% reduction from d 0 to 14 (P = 0.008) vs. CON. From d 0 to 42 the RAC fed steers tended to have a 0.24 kg/d greater ADG (P = 0.066) and tended to eat 4.27% less (P = 0.069) on a DM basis vs. CON. The RAC fed steers had a 19.95% greater gain to feed ratio compared to CON (P = 0.012). Steers fed RAC had an average of 12.52 kg greater HCW (P = 0.006) and an increase of 1.93 percentage units in dressing percent (P = 0.004) vs. CON. Ractopamine is an effective medicated feed additive for reducing NH3 and improving end product performance through HCW yields.

Effects of voluntary removal of ractopamine hydrochloride (Optaflexx) on live performance and carcass characteristics of beef steers

There is a lack of consistency across the globe in how countries establish tissue ractopamine residue limits and which residue limits are applied to various tissues, particularly for edible noncarcass tissues. Therefore, some US beef slaughter organizations have recommended a 48-h voluntary removal of ractopamine before slaughter in order to meet residue requirements of specific export countries and maintain international trade. Our objective was to assess the impact of voluntary removal of ractopamine hydrochloride (Optaflexx®; Elanco, Greenfield, IN) up to 8 d before slaughter on growth performance and carcass characteristics. Crossbred beef steers (60 pens of 10 animals/pen) with an initial shrunk body weight (BW) of 611.8 ± 10 kg SEM were fed one of six treatments over 42 d. Treatments included a control that did not receive ractopamine, on-label use of ractopamine (0-d withdrawal), and 2, 4, 6, or 8 d of voluntary removal of ractopamine from feed before slaughter. The start of ractopamine feeding (30.1 mg/kg of diet dry matter for 32 d) was staggered so that blocks could be slaughtered on the same day. Dry matter intake was decreased by 0.5 kg/d when ractopamine was fed with a 0-d withdrawal (P = 0.04) compared to the control, but was not altered (P = 0.56) as the duration of ractopamine removal increased from 0 to 8 d. Final BW, total BW gain, and average daily BW gain were increased by feeding ractopamine with a 0-d withdrawal (P = 0.09) compared to the control, but these variables decreased in a linear manner (P = 0.10) as the duration of removal increased from 0 to 8 d. Gain efficiency was improved by 15% (P &lt; 0.01) by feeding ractopamine with a 0-d withdrawal compared to the control, and gain efficiency decreased linearly (P = 0.06) as the duration of ractopamine removal increased. Approximately 2/3 of the increase in gain efficiency remained after 8 d of removal. Hot carcass weight was increased by 6 kg (P = 0.02) by feeding ractopamine with a 0-d withdrawal compared to the control. Measured carcass characteristics were not altered by ractopamine feeding or by removal before slaughter (P ≥ 0.24). The consequences of voluntary removal of ractopamine up to 8 d before slaughter were a linear decrease in live BW gain (0.64 kg/d), poorer gain efficiency, and numerically lighter carcass weight.

Effects of ractopamine hydrochloride on nutrient digestibility and nitrogen excretion of finishing beef cattle

The objective was to quantify the effects of the beta-adrenergic agonist (β-AA) ractopamine hydrochloride (Actogain, Zoetis, Parsippany, NJ) on nitrogen excretion and nutrient digestibility in feedlot cattle. In experiment 1, twelve Simmental × Angus steers were blocked by bodyweight (531 ± 16 kg) and used in a randomized complete block design. Dietary treatments included: 1) a control without β-AA (CON) or 2) 400 mg/steer/d ractopamine hydrochloride (RAC) for 35 d before slaughter. Diets contained (DM basis) 55% dry rolled corn, 20% corn silage, 15% modified wet distillers grains with solubles, and 10% supplement. For each block, total collection of feed, orts, feces and urine were conducted for two 5 d sampling periods during week 2 and 4 of RAC supplementation. No interaction (P &gt; 0.21) between treatment and collection period was observed for any parameter evaluated. Dietary treatment had no effect (P = 0.51) on DMI, but RAC had decreased fecal DM output (P = 0.04) compared with CON. Thus, RAC had greater apparent total tract DM digestibility (77.2 vs. 73.5%; P &lt; 0.01), N digestibility (72.4 vs. 69.4%; P = 0.01), and NDF digestibility (65.6 vs. 60.2%; P &lt; 0.01) than CON. Although treatment did not affect nitrogen intake (P = 0.52), RAC tended to reduce total nitrogen excretion (113.3 vs. 126.7 g/d; P = 0.10) compared with CON due to a tendency for decreased fecal nitrogen output (53.9 vs. 61.3 g/d; P = 0.10). However, dietary treatment had no effect (P = 0.53) on urinary nitrogen output or percentage of urinary nitrogen excreted as urea (P = 0.28). Experiment 2 was an in vitro experiment conducted to validate the effects of RAC on nutrient digestibility using Simmental × Angus heifers (451 ± 50 kg). Rumen fluid was collected individually by stomach tube from CON- (n = 9) and RAC-fed (n = 10) heifers to inoculate bottles containing a CON or RAC-containing substrate in a split-plot design. No interaction between rumen fluid source and in vitro substrate was observed. Greater IVDMD (P = 0.01) was observed in rumen fluid from RAC-fed heifers compared with rumen fluid from CON-fed heifers. Inclusion of RAC in the in vitro substrate increased IVDMD (P &lt; 0.01). Overall, feeding RAC increased microbial digestion of the dry-rolled corn-based finishing diet to increase total tract dry mater digestion by 5% and reduce nitrogen excretion by 10.6% in the 35 d period prior to slaughter.

Effects of differing withdrawal times from ractopamine hydrochloride on residue concentrations of beef muscle, adipose tissue, rendered tallow, and large intestine

Ractopamine hydrochloride (RAC) is a beta-agonist approved by the U.S. Food and Drug Administration (FDA) as a medicated feed ingredient for cattle during the final days of finishing to improve feed efficiency and growth. Maximum residue limits and U.S. FDA residue tolerances for target tissues have defined management practices around RAC usage in the U.S. However, many countries have adopted zero tolerance policies and testing of off-target tissues, presenting a major challenge for international export. Therefore, the objective this study was to determine the necessary withdrawal time among cattle group-fed RAC to achieve residue concentrations below tolerance levels in muscle and off-target tissues. Specifically, both total and parent RAC residues were quantified in muscle, adipose tissue, rendered tallow, and large intestines from animals group-fed RAC and subjected to withdrawal 2, 4, or 7 days before harvest. Ractopamine (parent and total) residues were below the assay limit of detection (< 0.12 ng/g) in all muscle and adipose tissue samples from animals in control groups (no RAC). However, RAC residues were detectable, but below the limit of quantitation, in 40% of tallow and 17% of large intestine samples from control animals. As expected, mean RAC residue concentrations in muscle, adipose tissue, and large intestine samples decreased (P < 0.05) as the RAC withdrawal duration (days) was extended. Irrespective of RAC withdrawal duration, mean parent RAC residue concentrations in muscle, adipose tissue, and large intestine ranged from 0.33 to 0.76 ng/g, 0.16 to 0.26 ng/g, 3.97 to 7.44 ng/g, respectively and all tallow samples were > 0.14 ng/g (detectable but below the limit of quantitation). Results of this study provide a baseline for the development of management protocol recommendations associated with withdrawal following group-feeding of RAC to beef cattle in countries that allow RAC use and intend to export to global markets which may be subject to zero tolerance policies and off-target tissue testing.