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.

Purpose A life cycle assessment was performed for the production of a total mixed ration (TMR) fed to finishing feedlot cattle in California, USA. The goal was to determine the climate change impact of the feed supply chain associated with the production of 1 kg finishing TMR (kg CO2e/kg TMR). A secondary goal was to compare the climate change impact of feed versus finished beef (kg CO2e/kg live weight). Methods The TMR was based on feeds commonly fed to finishing cattle in California. The Livestock Environmental Assessment and Performance Partnership (LEAP) guidelines were followed for inventory data collection. System boundaries included the production of crops and feed additives, transportation of TMR components, and compound feed production. Data were sourced from national databases and Ecoinvent™ unit process data. Three scenarios were assessed as a result of allocation at the transportation step: Scenario A (100% empty return load); Scenario B (50% empty return load): and Scenario C (0% empty return load). Energy, mass, and economic allocation, and system expansion of dried distillers grain solubles (DDGS) were assessed for sensitivity analysis. Total feedlot emission data from Stackhouse-Lawson et al. (2012) were used to compare to impacts of TMR production. Results Total emissions were determined to be 0.630 kg CO2e/kg TMR for Scenario A, 0.576 kg CO2e/kg TMR for Scenario B, and 0.521 kg CO2e/kg TMR for Scenario C. Corn production, transportation, and liquid premix production were primary contributors to the life cycle impacts of TMR production. Mass-based allocation of DDGS was found to have the most significant effect on overall impacts of the finishing TMR, with a 42% increase in life cycle emissions compared to other allocation methods. For Scenario A, feed used in Angus feedlot production contributed to 76% of total Angus feedlot emissions. Additionally, feed used in Holstein feedlot production contributed to 58% of total Holstein feedlot emissions. Conclusions and recommendations The present study demonstrates a need to better assess the feed supply chain of feedlot beef production in order to accurately identify areas that have the most significant impacts on overall emissions. This may aid in minimizing impacts associated with feed production and, by extension, beef production. The present study may also serve to inform future decisions for improvements or alterations of the LEAP guidelines.

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Feed additives have received increasing attention as a viable means to reduce enteric emissions from ruminants, which contribute to total anthropogenic methane (CH4) emissions. The aim of this study was to investigate the efficacy of the commercial feed additive SOP STAR COW (SOP) to reduce enteric emissions from dairy cows and to assess potential impacts on milk production. Twenty cows were blocked by parity and days in milk and randomly assigned to one of two treatment groups (n = 10): supplemented with 8 g/day SOP STAR COW, and an unsupplemented control group. Enteric emissions were measured in individual head chambers over a 12-h period, every 14 days for six weeks. SOP-treated cows over time showed a reduction in CH4 of 20.4% from day 14 to day 42 (p = 0.014), while protein % of the milk was increased (+4.9% from day 0 to day 14 (p = 0.036) and +6.5% from day 0 to day 42 (p = 0.002)). However, kg of milk protein remained similar within the SOP-treated cows over the trial period. The control and SOP-treated cows showed similar results for kg of milk fat and kg of milk protein produced per day. No differences in enteric emissions or milk parameters were detected between the control and SOP-treated cows on respective test days.

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