TY - JOUR
AU1 - Stackhouse-Lawson, K. R.
AU2 - Calvo, M. S.
AU3 - Place, S. E.
AU4 - Armitage, T. L.
AU5 - Pan, Y.
AU6 - Zhao, Y.
AU7 - Mitloehner, F. M.
AB - Abstract Increased animal productivity has the potential to reduce the environmental impact per unit of consumable product and is believed to be the most promising and sustainable mitigation technique to meet increasing demand for high quality protein. The feedlot industry uses ionophores, antibiotics, growth implants, and β2–adrenergic agonists to improve health and growth performance of cattle. These technologies not only increase productivity but also alter microbes in the rumen and increase nitrogen retention in the animal, which may lead to changes in greenhouse gas (GHG), volatile organic compound (VOC), and ammonia (NH3) emissions from feedlot cattle. The present study investigated GHG, VOC, and NH3 emissions from 160 Angus crossbred steers. Steers were blocked by weight in a randomized block design and assigned to 16 pens of 10 animals each. Treatments applied were 1) control (CON; no technology application), 2) monensin and tylosin phosphate (MON), 3) monensin, tylosin phosphate, and growth implant (IMP), and 4) monensin, tylosin phosphate, growth implant, and zilpaterol hydrochloride (fed during the last 20 d of the feeding period; BAA). Cattle were on feed for an average of 107 d. Performance variables (DMI, BW, ADG, and G:F) and carcass traits (HCW, dressing percent, KPH, LM area, fat thickness, marbling score, yield grade, and quality grade) were measured. Gaseous emissions were measured during the last 10 d of the feeding period when animals were housed in 4 totally enclosed identical cattle pen enclosures. To quantify gaseous emissions a 4 × 4 Latin square design (n = 4) was used. Gaseous emissions were analyzed using Proc Mixed in SAS and reported in grams per kilogram HCW per day and grams per kilogram per animal per hour. Treatment with IMP and BAA increased (P < 0.05) ADG, final BW, and HCW. Cattle on BAA had greater HCW and LM area (P < 0.05) and had lower (P < 0.05) CH4, methanol, and NH3 emissions per kilogram HCW than cattle on the remaining treatments. Methane emissions were similar for CON and IMP treated cattle. Nitrous oxide emissions were similar across CON, MON, and IMP treated cattle and were higher in BAA treated cattle (P < 0.05). The present study provides a better understanding of how application of growth promoting technologies to feedlot steers affects GHG, VOC, and NH3 emissions per kilogram of product. INTRODUCTION Beef cattle's contribution to greenhouse gas (GHG), ammonia (NH3), and smog-forming volatile organic compound (VOC) emissions are an increasing public policy concern. Improving cattle performance might be a viable gaseous emission mitigation strategy in beef production. The use of growth promoting technologies increases animal performance during the beef cattle stocker and finishing periods and may be a useful emission mitigation tool during those production phases. However, little information exists on actual emission reduction from greater animal productivity. Additionally, these technologies may alter rumenal microbial populations and shift metabolic function, changing nitrogen (N) retention in the animal, which may reduce GHG, NH3, and smog-forming VOC emissions. The main growth promoting technologies used in finishing operations are antibiotics, ionophores, anabolic implants, and β-adrenergic agonists. The largest improvements in animal performance are achieved through use of anabolic implants, which increase final BW while maintaining a similar body composition to nonimplanted steers (Guiroy et al., 2002). Ionophores and antibiotics are included in the diet of finishing cattle to improve animal health and feed efficiency. The β-adrenergic agonists are fed for the last 20 to 40 d of the finishing period to improve the efficiency of weight gain and increase lean muscle gain (Avendano-Reyes et al., 2006; Vasconcelos et al., 2008; Montgomery et al., 2009). These technologies are most often used in combination to maximize animal productivity. The objective of the present experiment was to evaluate the effects of growth promoting technologies on animal performance, carcass characteristics, and emission rates from feedlot cattle to provide a holistic assessment of their emission mitigation potential in beef production. Specific emission measurements include methane (CH4), nitrous oxide (N2O), carbon dioxide (CO2), methanol (MeOH), ethanol (EtOH), and NH3. MATERIALS AND METHODS The study was conducted at the University of California, Department of Animal Science's Feedlot and Environmental Quality Research Facility, located in Davis, CA, during July and December 2009. Steers were housed and managed in accordance to the Guide for the Care and Use of Agriculture Animals in Agriculture Research and Teaching (FASS, 1999) and the Animal Care and Use protocol for the University of California, Davis. Cattle, Housing, and Experimental Design A total of 160 Angus crossbred steers with an average initial BW of 436 ± 19.3 kg were used in an 86 to 128 d feeding study. Upon arrival to the commercial feedlot cattle were vaccinated with a modified live virus vaccine (Bovishield Gold; Zoetis Animal Health, New York, NY) and dewormed (Noromectrin; Norbrook Laboratories Limited, Down, North Ireland). Cattle were then shipped to the University of California, Davis, feedlot where they were allowed to acclimate to the experimental diet and facility for 2 wks. After the 2 wk acclimation period steers were blocked by weight and randomly allocated in a randomized block design into 1 of 16 pens with 10 animals per pen. Each pen had overhead shade oriented north to south and was equipped with an automatic float activated water trough. Pens had dimensions of 297 m2 and average linear bunk space of 120 cm. Pens were assigned to 1 of 4 treatments: 1) no feed additive or hormone implant [control (CON)], 2) 33.1 mg/kg DM of monensin (Rumensin; Elanco, Greenfield, IN) and 12.2 mg/kg DM of tylosin phosphate (Tylan; Elanco; MON), 3) 33.1 mg/kg DM of monensin, 12.2 mg/kg DM of tylosin phosphate, and implantation with a combination of 120 mg trenbolone acetate and 24 mg estradiol (Revalor-S; Intevet Inc., Millsboro, DE; IMP), and 4) 33.1 mg/kg DM of monensin, 12.2 mg/kg DM of tylosin phosphate, and implantation with a combination of 120 mg trenbolone acetate and 24 mg estradiol, supplemented with 8.3 mg/kg of DM of zilpaterol hydrochloride (ZH; Zilmax; Intervet Inc., Millsboro, DE; BAA). There were 3 experimental diets used during the study and they were prepared at the University of California, Department of Animal Science feedmill. All 3 experimental diets were exactly the same except for the addition of monensin, tylosin, and ZH as described in the treatments. Table 1 shows the ingredient and nutrient composition of the diet. All steers were fed the control diet during the 2-wk acclimation period (not containing monensin or tylosin). Zilpaterol hydrochloride was fed for the last 20 d of the feeding period. Before harvest, BAA treated steers were taken off ZH for 3 d to allow for the preharvest withdrawal time. During the trial steers were provided ad libitum access to water and diet. Cattle were harvested based on final shrunk body weight and differed by block. The heaviest BW block was on feed for 86 d and each of the remaining 3 BW blocks was harvested at 100, 114, and 128 d on feed. Table 1. Ingredient composition on an as-fed basis and analyzed nutrient content on a DM basis of diet for steers Item  Amount  Ingredient, as-fed basis, %        Steam flaked corn  77.5      Alfalfa hay  9.0      Dried distillers grain  4.0      Fat1  2.0      Premix2  7.5  Nutrient composition, DM basis, %      DM  93.1      CP  12.8      ADF ash free  7.6      NDF ash free  14.1      Ash  4.7      CF  6.3      Lignin ash free  1.6      Glucose3  0.5      Starch4  51.5      N  2.1      C  45.0      P  0.3      K  0.8      Ca  0.6      Mg  0.2  Item  Amount  Ingredient, as-fed basis, %        Steam flaked corn  77.5      Alfalfa hay  9.0      Dried distillers grain  4.0      Fat1  2.0      Premix2  7.5  Nutrient composition, DM basis, %      DM  93.1      CP  12.8      ADF ash free  7.6      NDF ash free  14.1      Ash  4.7      CF  6.3      Lignin ash free  1.6      Glucose3  0.5      Starch4  51.5      N  2.1      C  45.0      P  0.3      K  0.8      Ca  0.6      Mg  0.2  1Yellow grease. 2Included mineral mix and soybean meal carrier for Tylan and Monensin at 33.1 and 12.2 mg/kg DM, respectively. 3Total glucose of total nonstructural carbohydrates is the sum of total glucose, free fructose, and free sucrose. 4Starch is the total glucose minus the free glucose multiplied by 0.09 (ANR, 2006). View Large Table 1. Ingredient composition on an as-fed basis and analyzed nutrient content on a DM basis of diet for steers Item  Amount  Ingredient, as-fed basis, %        Steam flaked corn  77.5      Alfalfa hay  9.0      Dried distillers grain  4.0      Fat1  2.0      Premix2  7.5  Nutrient composition, DM basis, %      DM  93.1      CP  12.8      ADF ash free  7.6      NDF ash free  14.1      Ash  4.7      CF  6.3      Lignin ash free  1.6      Glucose3  0.5      Starch4  51.5      N  2.1      C  45.0      P  0.3      K  0.8      Ca  0.6      Mg  0.2  Item  Amount  Ingredient, as-fed basis, %        Steam flaked corn  77.5      Alfalfa hay  9.0      Dried distillers grain  4.0      Fat1  2.0      Premix2  7.5  Nutrient composition, DM basis, %      DM  93.1      CP  12.8      ADF ash free  7.6      NDF ash free  14.1      Ash  4.7      CF  6.3      Lignin ash free  1.6      Glucose3  0.5      Starch4  51.5      N  2.1      C  45.0      P  0.3      K  0.8      Ca  0.6      Mg  0.2  1Yellow grease. 2Included mineral mix and soybean meal carrier for Tylan and Monensin at 33.1 and 12.2 mg/kg DM, respectively. 3Total glucose of total nonstructural carbohydrates is the sum of total glucose, free fructose, and free sucrose. 4Starch is the total glucose minus the free glucose multiplied by 0.09 (ANR, 2006). View Large Performance Body weights were measured every 28 d before the morning feeding using a chute with calibrated scale (Silencer; Commercial Pro Model, Lorraine, KS). Steers were also weighed when they were moved into the cattle pen enclosures (CPE) on d 1 of the gas sampling period and the morning on d 11 of the gas sampling period when they were removed from the CPE. The diet was fed twice daily at 0700 and 1400 h and in a 60:40 proportion. Feed bunks were evaluated at 0600 h; feed remaining in the bunk was estimated, and the daily allotment of feed was determined. Feed intake was determined on a per pen basis. Carcass Traits Steers were harvested at a commercial abattoir; USDA graders and trained personnel gathering carcass data were blind to treatments. Carcasses were chilled at –3°C for approximately 24 h after harvest, at which time carcass characteristics and USDA quality and yield grades were obtained. Carcass measurements included KPH, fat thickness, marbling score, longissimus muscle area, and HCW. Yield grade and dressing percent were calculated according to USDA guidelines (USDA, 1997). Gas Sampling On d 10 of ZH treatment (13 d before harvest), steers were moved into the CPE facility, which allowed for simultaneous air emission testing of the 4 mitigation treatments. During air emission sampling the statistical design was a 4 × 4 Latin square to ensure that each CPE experienced every treatment in a random and unbiased fashion. The CPE facility consisted of 4 totally enclosed 185 m2 dirt-floored pens each with a 13 m2 concrete feed apron located on the west side and float-activated water trough on the east side of each corral. A hinged feed flap along the bunk was used on the west side for feed delivery in each corral. The remainder of the corral was dirt floored with a 3% slope. Each CPE is a dome-like, 22 by 11 m structure constructed with a steel frame, welded truss arches with parallel steel tubes, and continuous structural webbing (11 m Legend Series Cover-All Building; Saskatoon, Saskatchewan, Canada). The steel structure was covered with a white 100% Marquesa Lana double stacked weave Dura-Weave cover (Intertape Polymer Group, Montreal, Quebec, Canada). Each CPE was equipped with a 4.88 by 1.22 m cooling pad on the east side to allow ambient air inflow and evaporative cooling. Two fans with ventilation openings on the west side provide air outflow. Fan speed and cooling pad operation were controllable inside the CPE. Fan revolutions per minute (RPM) was monitored constantly by 2 optical sensors (Monarch Instruments, Amherst, NH) mounted on every fan unit in each CPE. The RPM of each fan and the static differential pressure between inside and outside CPE were recorded to determine air flow on 10 min intervals using data loggers (Onset Computer Corporation, Bourne, MA). The fans create a negative pressure by venting air out of the corral providing directional airflow from east to west in each CPE. The CPE were calibrated as described in Cooprider et al. (2011). The photoacoustic field gas monitor, an Innova model 1412 (Innova AirTech Instruments, Ballerup, Denmark), was used to continuously measure EtOH, MeOH, NH3, CO2, and N2O. The Innova gas analyzer selectively measures up to 5 component gases and water vapor simultaneously using optical filters. The TEI 55C Direct Methane Non-Methane Hydrocarbon analyzer (Thermo Environmental Instruments, Waltham, MA) was used to measure CH4. The TEI 55C measures CH4 using a back-flush gas chromatography system designed for automated measurement of methane and nonmethane hydrocarbons. Measurements in 20 min intervals were obtained in sequential order starting with the inlet and followed by the 4 outlet locations of the CPE units. The Innova 1412 and TEI 55C continuously measured gas concentrations at 1-min intervals. The air sampling equipment was located centrally, in an air conditioned cabinet, between the second and the third CPE. For each CPE, 48.8 m of Teflon tubing (12.7 mm i.d.) was used to connect the CPE sampling location to the Innova 1412 and TEI 55C. Net emissions were calculated as the concentration difference between the air outlet and inlet multiplied by the ventilation rate. Data corresponding to short time interruptions in which the CPE was opened for feeding or entry were omitted for calculation of emission fluxes. Cattle pen enclosures were thoroughly cleaned before each replicate herd entered for emission monitoring. Emission rates were reported in grams per kilogram HCW per day to most effectively represent different management techniques for greater production efficiencies as they impact emissions of VOC, NH3, and GHG. Emission rates are also reported in grams per animal per hour for ease of emission comparisons. Meteorological Measures Ambient temperature (°C) and relative humidity (%) were measured continuously (10 min intervals) within each CPE using data loggers (HOBO Pro Data Logger Series; Onset Computer Corporation, Bourne, MA; Table 2). Meteorological measurements were obtained outside the CPE using an automatic weather station (Model 110-WS-16; Novalynx, Auburn, CA), which was centrally located at the east end of the CPE. Measures were recorded in 15 min intervals and included ambient temperature (°C), black globe temperature, relative humidity (%), and wind velocity (m/s; Table 2). Table 2. Average meteorological measures for outdoor and indoor cattle pen enclosures (CPE) during the gaseous emission measurement period   Replication  Item  1  2  3  4  Outside      Wind velocity, m/s  1.07 ± 0.88  1.0 ± 0.89  1.19 ± 1.20  1.01 ± 1.06      Relative humidity, %  41.1 ± 19.65  58.6 ± 23.13  61.9 ± 22.06  61.0 ± 20.48      Ambient temperature  20.4 ± 7.75  17.1 ± 5.23  16.3 ± 4.99  12.4 ± 5.40      Black globe temperature  22.2 ± 9.11  18.6 ± 6.68  17.6 ± 6.48  13.4 ± 6.89  CPE ambient temperature1      CPE 1  15.3 ± 5.27  17.6 ± 4.20  15.0 ± 5.63  12.2 ± 4.58      CPE 2  15.1 ± 5.16  17.6 ± 4.34  14.8 ± 5.56  12.6 ± 4.62      CPE 3  16.1 ± 5.59  17.9 ± 4.24  15.2 ± 5.47  12.8 ± 4.28      CPE 4  15.3 ± 5.11  17.4 ± 4.06  15.2 ± 5.25  12.3 ± 4.75  CPE relative humidity, %      CPE 1  82.6 ± 17.52  92.5 ± 18.99  78.2 ± 21.66  79.2 ± 20.23      CPE 2  85.1 ± 18.36  94.3 ± 19.12  80.2 ± 23.19  81.3 ± 21.67      CPE 3  88.6 ± 19.18  97.8 ± 15.56  85.4 ± 23.60  84.3 ± 23.48      CPE 4  88.7 ± 18.63  97.2 ± 16.93  85.9 ± 26.11  85.8 ± 24.39    Replication  Item  1  2  3  4  Outside      Wind velocity, m/s  1.07 ± 0.88  1.0 ± 0.89  1.19 ± 1.20  1.01 ± 1.06      Relative humidity, %  41.1 ± 19.65  58.6 ± 23.13  61.9 ± 22.06  61.0 ± 20.48      Ambient temperature  20.4 ± 7.75  17.1 ± 5.23  16.3 ± 4.99  12.4 ± 5.40      Black globe temperature  22.2 ± 9.11  18.6 ± 6.68  17.6 ± 6.48  13.4 ± 6.89  CPE ambient temperature1      CPE 1  15.3 ± 5.27  17.6 ± 4.20  15.0 ± 5.63  12.2 ± 4.58      CPE 2  15.1 ± 5.16  17.6 ± 4.34  14.8 ± 5.56  12.6 ± 4.62      CPE 3  16.1 ± 5.59  17.9 ± 4.24  15.2 ± 5.47  12.8 ± 4.28      CPE 4  15.3 ± 5.11  17.4 ± 4.06  15.2 ± 5.25  12.3 ± 4.75  CPE relative humidity, %      CPE 1  82.6 ± 17.52  92.5 ± 18.99  78.2 ± 21.66  79.2 ± 20.23      CPE 2  85.1 ± 18.36  94.3 ± 19.12  80.2 ± 23.19  81.3 ± 21.67      CPE 3  88.6 ± 19.18  97.8 ± 15.56  85.4 ± 23.60  84.3 ± 23.48      CPE 4  88.7 ± 18.63  97.2 ± 16.93  85.9 ± 26.11  85.8 ± 24.39  1Steers were placed in CPE on d 73, 87, 101, and 115 of the feeding period for replication 1, 2, 3, and 4, respectively. View Large Table 2. Average meteorological measures for outdoor and indoor cattle pen enclosures (CPE) during the gaseous emission measurement period   Replication  Item  1  2  3  4  Outside      Wind velocity, m/s  1.07 ± 0.88  1.0 ± 0.89  1.19 ± 1.20  1.01 ± 1.06      Relative humidity, %  41.1 ± 19.65  58.6 ± 23.13  61.9 ± 22.06  61.0 ± 20.48      Ambient temperature  20.4 ± 7.75  17.1 ± 5.23  16.3 ± 4.99  12.4 ± 5.40      Black globe temperature  22.2 ± 9.11  18.6 ± 6.68  17.6 ± 6.48  13.4 ± 6.89  CPE ambient temperature1      CPE 1  15.3 ± 5.27  17.6 ± 4.20  15.0 ± 5.63  12.2 ± 4.58      CPE 2  15.1 ± 5.16  17.6 ± 4.34  14.8 ± 5.56  12.6 ± 4.62      CPE 3  16.1 ± 5.59  17.9 ± 4.24  15.2 ± 5.47  12.8 ± 4.28      CPE 4  15.3 ± 5.11  17.4 ± 4.06  15.2 ± 5.25  12.3 ± 4.75  CPE relative humidity, %      CPE 1  82.6 ± 17.52  92.5 ± 18.99  78.2 ± 21.66  79.2 ± 20.23      CPE 2  85.1 ± 18.36  94.3 ± 19.12  80.2 ± 23.19  81.3 ± 21.67      CPE 3  88.6 ± 19.18  97.8 ± 15.56  85.4 ± 23.60  84.3 ± 23.48      CPE 4  88.7 ± 18.63  97.2 ± 16.93  85.9 ± 26.11  85.8 ± 24.39    Replication  Item  1  2  3  4  Outside      Wind velocity, m/s  1.07 ± 0.88  1.0 ± 0.89  1.19 ± 1.20  1.01 ± 1.06      Relative humidity, %  41.1 ± 19.65  58.6 ± 23.13  61.9 ± 22.06  61.0 ± 20.48      Ambient temperature  20.4 ± 7.75  17.1 ± 5.23  16.3 ± 4.99  12.4 ± 5.40      Black globe temperature  22.2 ± 9.11  18.6 ± 6.68  17.6 ± 6.48  13.4 ± 6.89  CPE ambient temperature1      CPE 1  15.3 ± 5.27  17.6 ± 4.20  15.0 ± 5.63  12.2 ± 4.58      CPE 2  15.1 ± 5.16  17.6 ± 4.34  14.8 ± 5.56  12.6 ± 4.62      CPE 3  16.1 ± 5.59  17.9 ± 4.24  15.2 ± 5.47  12.8 ± 4.28      CPE 4  15.3 ± 5.11  17.4 ± 4.06  15.2 ± 5.25  12.3 ± 4.75  CPE relative humidity, %      CPE 1  82.6 ± 17.52  92.5 ± 18.99  78.2 ± 21.66  79.2 ± 20.23      CPE 2  85.1 ± 18.36  94.3 ± 19.12  80.2 ± 23.19  81.3 ± 21.67      CPE 3  88.6 ± 19.18  97.8 ± 15.56  85.4 ± 23.60  84.3 ± 23.48      CPE 4  88.7 ± 18.63  97.2 ± 16.93  85.9 ± 26.11  85.8 ± 24.39  1Steers were placed in CPE on d 73, 87, 101, and 115 of the feeding period for replication 1, 2, 3, and 4, respectively. View Large Manure Measurements Feces redox potential and pH were taken on d 6 and 11 from the dirt floor of CPE housing for each experimental period. Measurements were taken using a portable pH and redox potential meter (acorn series 6; Oakton, Vernon Hills, IL) after the morning feeding in 10 different grid locations to ensure a representative sample of the entire CPE. Ground surface temperature was measured across the same 10 grid locations using a laser thermometer gun (Raynger ST; Raytek, Santa Cruz, CA). Statistical Analysis Gaseous emission data (MeOH, EtOH, CO2, N2O, NH3, and CH4) were analyzed using repeated measures PROC MIXED in SAS version 9.1 (SAS Inst. Inc., Cary, NC) with a significance level of P < 0.05. The least squares means statement was used to determine treatment differences. Time was treated as a covariate; replication and CPE were treated as random variables. Performance variables were analyzed using the ANOVA procedure in SAS version 9.1, as a completely randomized design with treatment as the independent variable. Soil pH and soil redox potential at d 6 and 11 were analyzed as a Latin square split plot using the ANOVA procedure in SAS version 9.1. For quality grades the CATMOD procedure in SAS was used with categorical animal data averaged per treatment. For all models, treatment was the independent variable of interest. RESULTS Performance Initial BW was similar for all treated groups (P = 0.56; Table 3). Final BW was greater for the BAA and IMP (P < 0.0001) steers compared to CON and MON treated steers. Cattle that were treated with an anabolic implant (IMP and BAA) had a respective 24 and 28% increase in ADG compared to nonimplanted (CON and MON) steers (P < 0.0001) and improved G:F (P < 0.0001). There was no difference in DMI across treatments. Table 3. Least squares means of feedlot performance and carcass characteristics of steers treated with different technology applications   Treatment      Item  CON1  MON2  IMP3  BAA4  SEM  P-value  Performance parameters      Number of pens  4  4  4  4          Number of steers  40  40  40  40          Initial BW, kg  434  435  439  436  11  0.56      Final BW, kg  574a  575a  623b  628b  7.3  0.0001      ADG, kg/d  1.33a  1.30a  1.72b  1.80b  0.07  0.0001      DMI, kg/d  10.2  9.9  10.1  10.6  0.39  0.57      G:F  0.131a  0.132a  0.171b  0.169b  0.005  0.0001  Carcass characteristics      Number of carcasses  40  40  40  40          HCW, kg  361a  357a  385b  400c  4.17  0.0001      Dressing percent  62.5a  62.1a  62.3a,b  63.5b  0.39  0.048      Fat thickness, cm  1.47  1.66  1.51  1.59  0.10  0.45      Marbling score5  487  485  466  464  22  0.38      LM, cm  81.1a  79.9a  85.6b  92.3c  1.84  0.0001      KPH, %  1.96  1.97  2.01  1.95  0.04  0.28      USDA yield grade  3.34  3.56  3.36  3.22  0.13  0.31  Quality grade      Select, %  12.5  7.5  17.1  21.2    0.43      Choice, %  87.5  92.5  82.9  78.8    0.43    Treatment      Item  CON1  MON2  IMP3  BAA4  SEM  P-value  Performance parameters      Number of pens  4  4  4  4          Number of steers  40  40  40  40          Initial BW, kg  434  435  439  436  11  0.56      Final BW, kg  574a  575a  623b  628b  7.3  0.0001      ADG, kg/d  1.33a  1.30a  1.72b  1.80b  0.07  0.0001      DMI, kg/d  10.2  9.9  10.1  10.6  0.39  0.57      G:F  0.131a  0.132a  0.171b  0.169b  0.005  0.0001  Carcass characteristics      Number of carcasses  40  40  40  40          HCW, kg  361a  357a  385b  400c  4.17  0.0001      Dressing percent  62.5a  62.1a  62.3a,b  63.5b  0.39  0.048      Fat thickness, cm  1.47  1.66  1.51  1.59  0.10  0.45      Marbling score5  487  485  466  464  22  0.38      LM, cm  81.1a  79.9a  85.6b  92.3c  1.84  0.0001      KPH, %  1.96  1.97  2.01  1.95  0.04  0.28      USDA yield grade  3.34  3.56  3.36  3.22  0.13  0.31  Quality grade      Select, %  12.5  7.5  17.1  21.2    0.43      Choice, %  87.5  92.5  82.9  78.8    0.43  a–cWithin a row least squares means without common subscript letters differ (P < 0.05). 1CON = no feed additive or hormone implant. 2MON = 33.1 mg/kg DM of monensin (Rumensin; Elanco, Greenfield, IN) and 12.2 mg/kg DM of tylosin phosphate (Tylan; Elanco, Greenfield, IN). 3IMP = 33.1 mg/kg DM of monensin, 12.2 mg/kg DM of tylosin phosphate, and implantation with a combination of 120 mg trenbolone acetate and 24 mg estradiol (Revalor-S; Intevet Inc., Millsboro, DE). 4BAA = 33.1 mg/kg DM of monensin, 12.2 mg/kg DM of tylosin phosphate, implantation with a combination of 120 mg trenbolone acetate and 24 mg estradiol, and supplemented with 8.3 mg/kg of DM of zilpaterol hydrochloride (Zilmax; Intervet Inc., Millsboro, DE) during the last 20 d on feed. 5Marbling scores: 300 = slight00; 400 = small00; 500 = modest00. View Large Table 3. Least squares means of feedlot performance and carcass characteristics of steers treated with different technology applications   Treatment      Item  CON1  MON2  IMP3  BAA4  SEM  P-value  Performance parameters      Number of pens  4  4  4  4          Number of steers  40  40  40  40          Initial BW, kg  434  435  439  436  11  0.56      Final BW, kg  574a  575a  623b  628b  7.3  0.0001      ADG, kg/d  1.33a  1.30a  1.72b  1.80b  0.07  0.0001      DMI, kg/d  10.2  9.9  10.1  10.6  0.39  0.57      G:F  0.131a  0.132a  0.171b  0.169b  0.005  0.0001  Carcass characteristics      Number of carcasses  40  40  40  40          HCW, kg  361a  357a  385b  400c  4.17  0.0001      Dressing percent  62.5a  62.1a  62.3a,b  63.5b  0.39  0.048      Fat thickness, cm  1.47  1.66  1.51  1.59  0.10  0.45      Marbling score5  487  485  466  464  22  0.38      LM, cm  81.1a  79.9a  85.6b  92.3c  1.84  0.0001      KPH, %  1.96  1.97  2.01  1.95  0.04  0.28      USDA yield grade  3.34  3.56  3.36  3.22  0.13  0.31  Quality grade      Select, %  12.5  7.5  17.1  21.2    0.43      Choice, %  87.5  92.5  82.9  78.8    0.43    Treatment      Item  CON1  MON2  IMP3  BAA4  SEM  P-value  Performance parameters      Number of pens  4  4  4  4          Number of steers  40  40  40  40          Initial BW, kg  434  435  439  436  11  0.56      Final BW, kg  574a  575a  623b  628b  7.3  0.0001      ADG, kg/d  1.33a  1.30a  1.72b  1.80b  0.07  0.0001      DMI, kg/d  10.2  9.9  10.1  10.6  0.39  0.57      G:F  0.131a  0.132a  0.171b  0.169b  0.005  0.0001  Carcass characteristics      Number of carcasses  40  40  40  40          HCW, kg  361a  357a  385b  400c  4.17  0.0001      Dressing percent  62.5a  62.1a  62.3a,b  63.5b  0.39  0.048      Fat thickness, cm  1.47  1.66  1.51  1.59  0.10  0.45      Marbling score5  487  485  466  464  22  0.38      LM, cm  81.1a  79.9a  85.6b  92.3c  1.84  0.0001      KPH, %  1.96  1.97  2.01  1.95  0.04  0.28      USDA yield grade  3.34  3.56  3.36  3.22  0.13  0.31  Quality grade      Select, %  12.5  7.5  17.1  21.2    0.43      Choice, %  87.5  92.5  82.9  78.8    0.43  a–cWithin a row least squares means without common subscript letters differ (P < 0.05). 1CON = no feed additive or hormone implant. 2MON = 33.1 mg/kg DM of monensin (Rumensin; Elanco, Greenfield, IN) and 12.2 mg/kg DM of tylosin phosphate (Tylan; Elanco, Greenfield, IN). 3IMP = 33.1 mg/kg DM of monensin, 12.2 mg/kg DM of tylosin phosphate, and implantation with a combination of 120 mg trenbolone acetate and 24 mg estradiol (Revalor-S; Intevet Inc., Millsboro, DE). 4BAA = 33.1 mg/kg DM of monensin, 12.2 mg/kg DM of tylosin phosphate, implantation with a combination of 120 mg trenbolone acetate and 24 mg estradiol, and supplemented with 8.3 mg/kg of DM of zilpaterol hydrochloride (Zilmax; Intervet Inc., Millsboro, DE) during the last 20 d on feed. 5Marbling scores: 300 = slight00; 400 = small00; 500 = modest00. View Large Carcass Traits Treatment with an anabolic implant resulted in greater HCW for IMP vs. CON and MON treated steers by an average of 25.7 kg (P < 0.001; Table 3). Hot carcass weight was greatest for BAA steers (P < 0.001). The LM area was largest in the BAA treated steers, resulting in a 6.7 cm2 greater area compared to the IMP treated cattle (P < 0.001) and 11.2 and 12.4 cm2 compared to the CON and MON treatments (P < 0.001). Dressing percent was greater by 1% (P < 0.048) for the BAA compared to CON and MON treated cattle. There was no difference across treatments for fat thickness, marbling score, KPH, yield grade, or quality grade distribution. Gaseous Emission Measurements When emissions were calculated based on gram per kilogram HCW per day cattle in the MON treatment had lower CH4 emissions per kilogram HCW (P < 0.001) compared to those in the CON and IMP treatments (Table 4). During the last 10 d of the feeding period, steers treated with BAA had an 8, 14, and 16% lower CH4 emissions/kg HCW when compared to the MON, CON, and IMP treatments, respectively (P < 0.0001). Methane emissions in grams per kilogram HCW per day were similar for CON and IMP treated cattle. Nitrous oxide emissions in grams per kilogram HCW per day were similar across CON, MON, and IMP treated cattle and were higher in BAA treated cattle (P < 0.0001). Carbon dioxide reported as grams per kilogram HCW per day was similar across treatments. Ethanol emissions (g · kg HCW–1 · d–1) for the CON, IMP, and BAA treated steers were similar and EtOH emissions for IMP and MON were similar. Cattle treated with MON had higher EtOH emissions than CON and BAA treated steers (P < 0.01). Methanol emissions in grams per kilogram HCW per day were lowest from BAA treated steers (P < 0.006) when compared to all other treatments. Ammonia emissions (g · kg HCW–1 · d–1) differed across all treatments (P < 0.0001). Cattle treated with BAA had 20, 37, and 43% lower NH3 emissions (g · kg HCW–1 · d–1) than CON, MON, and IMP treated steers, respectively. Table 4. Least squares means of methane (CH4), nitrous oxide (N2O), carbon dioxide (CO2), ethanol (EtOH), methanol (MeOH), and ammonia (NH3) emissions reported in grams per kilogram HCW per day from feedlot steers treated with different technology applications   Treatment      Emission, g · kg HCW–1 · d–1  CON1  MON2  IMP3  BAA4  SEM  P-value  CH4  0.73c  0.66b  0.71c  0.61a  0.06  0.0001  N2O  0.015a  0.015a  0.016a  0.018b  0.002  0.0001  CO2  65  64  66  65  6.0  0.09  EtOH  0.015a  0.046b  0.030a,b  0.017a  0.02  0.01  MeOH  0.0035b  0.0033b  0.0029b  0.0019a  0.00002  0.0006  NH3  0.27b  0.30c  0.33d  0.19a  0.04  0.0001    Treatment      Emission, g · kg HCW–1 · d–1  CON1  MON2  IMP3  BAA4  SEM  P-value  CH4  0.73c  0.66b  0.71c  0.61a  0.06  0.0001  N2O  0.015a  0.015a  0.016a  0.018b  0.002  0.0001  CO2  65  64  66  65  6.0  0.09  EtOH  0.015a  0.046b  0.030a,b  0.017a  0.02  0.01  MeOH  0.0035b  0.0033b  0.0029b  0.0019a  0.00002  0.0006  NH3  0.27b  0.30c  0.33d  0.19a  0.04  0.0001  a–dWithin row least squares means without common subscript letters differ (P < 0.05). 1CON = no feed additive or hormone implant. 2MON = 33.1 mg/kg DM of monensin (Rumensin; Elanco, Greenfield, IN) and 12.2 mg/kg DM of tylosin phosphate (Tylan; Elanco, Greenfield, IN). 3IMP = 33.1 mg/kg DM of monensin, 12.2 mg/kg DM of tylosin phosphate, and implantation with a combination of 120 mg trenbolone acetate and 24 mg estradiol (Revalor-S; Intevet Inc., Millsboro, DE). 4BAA = 33.1 mg/kg DM of monensin, 12.2 mg/kg DM of tylosin phosphate, implantation with a combination of 120 mg trenbolone acetate and 24 mg estradiol, and supplemented with 8.3 mg/kg of DM of zilpaterol hydrochloride (Zilmax; Intervet Inc., Millsboro, DE). View Large Table 4. Least squares means of methane (CH4), nitrous oxide (N2O), carbon dioxide (CO2), ethanol (EtOH), methanol (MeOH), and ammonia (NH3) emissions reported in grams per kilogram HCW per day from feedlot steers treated with different technology applications   Treatment      Emission, g · kg HCW–1 · d–1  CON1  MON2  IMP3  BAA4  SEM  P-value  CH4  0.73c  0.66b  0.71c  0.61a  0.06  0.0001  N2O  0.015a  0.015a  0.016a  0.018b  0.002  0.0001  CO2  65  64  66  65  6.0  0.09  EtOH  0.015a  0.046b  0.030a,b  0.017a  0.02  0.01  MeOH  0.0035b  0.0033b  0.0029b  0.0019a  0.00002  0.0006  NH3  0.27b  0.30c  0.33d  0.19a  0.04  0.0001    Treatment      Emission, g · kg HCW–1 · d–1  CON1  MON2  IMP3  BAA4  SEM  P-value  CH4  0.73c  0.66b  0.71c  0.61a  0.06  0.0001  N2O  0.015a  0.015a  0.016a  0.018b  0.002  0.0001  CO2  65  64  66  65  6.0  0.09  EtOH  0.015a  0.046b  0.030a,b  0.017a  0.02  0.01  MeOH  0.0035b  0.0033b  0.0029b  0.0019a  0.00002  0.0006  NH3  0.27b  0.30c  0.33d  0.19a  0.04  0.0001  a–dWithin row least squares means without common subscript letters differ (P < 0.05). 1CON = no feed additive or hormone implant. 2MON = 33.1 mg/kg DM of monensin (Rumensin; Elanco, Greenfield, IN) and 12.2 mg/kg DM of tylosin phosphate (Tylan; Elanco, Greenfield, IN). 3IMP = 33.1 mg/kg DM of monensin, 12.2 mg/kg DM of tylosin phosphate, and implantation with a combination of 120 mg trenbolone acetate and 24 mg estradiol (Revalor-S; Intevet Inc., Millsboro, DE). 4BAA = 33.1 mg/kg DM of monensin, 12.2 mg/kg DM of tylosin phosphate, implantation with a combination of 120 mg trenbolone acetate and 24 mg estradiol, and supplemented with 8.3 mg/kg of DM of zilpaterol hydrochloride (Zilmax; Intervet Inc., Millsboro, DE). View Large Emissions were also calculated as grams per animal per hour. Methane emissions on a per animal basis were also lowest in the MON and BAA treated cattle and were similar between the BAA and CON treated cattle and the CON and IMP treated cattle (P < 0.0001; Table 5). Nitrous oxide per animal was lowest in the IMP, MON, and CON treated cattle and the MON and CON were similar to the BAA treated cattle (P < 0.0001; Table 5). Carbon dioxide and EtOH was similar across treatment groups (Table 5). Ammonia was lowest in the BAA treated cattle and similar between the CON and IMP treated cattle and the IMP and MON treated cattle (P < 0.001; Table 5). Overall, treatment with BAA resulted in 42, 46, and 47% lower NH3 emissions, respectively. Table 5. Least squares means of methane (CH4), nitrous oxide (N2O), carbon dioxide (CO2), ethanol (EtOH), methanol (MeOH), and ammonia (NH3) emissions reported in grams per animal per hour from feedlot steers treated with different technology applications   Treatment      Emission, g · animal–1 · h–1  CON1  MON2  IMP3  BAA4  SEM  P-value  CH4  11.1b,c  9.96a  11.36c  10.16a,b  10.0  0.0001  N2O  0.250a,b  0.246a,b  0.236a  0.289b  0.04  0.0001  CO2  1,008  988  1,027  1,056  10  0.07  EtOH  0.559  0.484  0.789  0.552  0.4  0.07  MeOH  0.0445a,b  0.0437a,b  0.0555b  0.0386a  0.002  0.05  NH3  4.54b  4.91c  4.81b,c  2.63a  0.6  0.0001    Treatment      Emission, g · animal–1 · h–1  CON1  MON2  IMP3  BAA4  SEM  P-value  CH4  11.1b,c  9.96a  11.36c  10.16a,b  10.0  0.0001  N2O  0.250a,b  0.246a,b  0.236a  0.289b  0.04  0.0001  CO2  1,008  988  1,027  1,056  10  0.07  EtOH  0.559  0.484  0.789  0.552  0.4  0.07  MeOH  0.0445a,b  0.0437a,b  0.0555b  0.0386a  0.002  0.05  NH3  4.54b  4.91c  4.81b,c  2.63a  0.6  0.0001  a–cWithin row least squares means without common subscript letters differ (P < 0.05). 1CON = no feed additive or hormone implant. 2MON = 33.1 mg/kg DM of monensin (Rumensin; Elanco, Greenfield, IN) and 12.2 mg/kg DM of tylosin phosphate (Tylan; Elanco, Greenfield, IN). 3IMP = 33.1 mg/kg DM of monensin, 12.2 mg/kg DM of tylosin phosphate, and implantation with a combination of 120 mg trenbolone acetate and 24 mg estradiol (Revalor-S; Intevet Inc., Millsboro, DE). 4BAA = 33.1 mg/kg DM of monensin, 12.2 mg/kg DM of tylosin phosphate, implantation with a combination of 120 mg trenbolone acetate and 24 mg estradiol, and supplemented with 8.3 mg/kg of DM of zilpaterol hydrochloride (Zilmax; Intervet Inc., Millsboro, DE). View Large Table 5. Least squares means of methane (CH4), nitrous oxide (N2O), carbon dioxide (CO2), ethanol (EtOH), methanol (MeOH), and ammonia (NH3) emissions reported in grams per animal per hour from feedlot steers treated with different technology applications   Treatment      Emission, g · animal–1 · h–1  CON1  MON2  IMP3  BAA4  SEM  P-value  CH4  11.1b,c  9.96a  11.36c  10.16a,b  10.0  0.0001  N2O  0.250a,b  0.246a,b  0.236a  0.289b  0.04  0.0001  CO2  1,008  988  1,027  1,056  10  0.07  EtOH  0.559  0.484  0.789  0.552  0.4  0.07  MeOH  0.0445a,b  0.0437a,b  0.0555b  0.0386a  0.002  0.05  NH3  4.54b  4.91c  4.81b,c  2.63a  0.6  0.0001    Treatment      Emission, g · animal–1 · h–1  CON1  MON2  IMP3  BAA4  SEM  P-value  CH4  11.1b,c  9.96a  11.36c  10.16a,b  10.0  0.0001  N2O  0.250a,b  0.246a,b  0.236a  0.289b  0.04  0.0001  CO2  1,008  988  1,027  1,056  10  0.07  EtOH  0.559  0.484  0.789  0.552  0.4  0.07  MeOH  0.0445a,b  0.0437a,b  0.0555b  0.0386a  0.002  0.05  NH3  4.54b  4.91c  4.81b,c  2.63a  0.6  0.0001  a–cWithin row least squares means without common subscript letters differ (P < 0.05). 1CON = no feed additive or hormone implant. 2MON = 33.1 mg/kg DM of monensin (Rumensin; Elanco, Greenfield, IN) and 12.2 mg/kg DM of tylosin phosphate (Tylan; Elanco, Greenfield, IN). 3IMP = 33.1 mg/kg DM of monensin, 12.2 mg/kg DM of tylosin phosphate, and implantation with a combination of 120 mg trenbolone acetate and 24 mg estradiol (Revalor-S; Intevet Inc., Millsboro, DE). 4BAA = 33.1 mg/kg DM of monensin, 12.2 mg/kg DM of tylosin phosphate, implantation with a combination of 120 mg trenbolone acetate and 24 mg estradiol, and supplemented with 8.3 mg/kg of DM of zilpaterol hydrochloride (Zilmax; Intervet Inc., Millsboro, DE). View Large Manure Measurements There were no treatment differences for manure pH or redox potential during CPE housing (Table 6). Table 6. Average daily manure pH and reduction potential ± standard deviation by treatment   Treatment    Item  CON1  MON2  IMP3  BAA4  P-value  Manure pH  6.7 ± 0.4  6.7 ± 0.4  6.8 ± 0.6  6.7 ± 0.4  0.49  Manure redox potential, mV  95.3 ± 65.7  122.5 ± 50.5  131.7 ± 53.4  89.0 ± 71.1  0.34    Treatment    Item  CON1  MON2  IMP3  BAA4  P-value  Manure pH  6.7 ± 0.4  6.7 ± 0.4  6.8 ± 0.6  6.7 ± 0.4  0.49  Manure redox potential, mV  95.3 ± 65.7  122.5 ± 50.5  131.7 ± 53.4  89.0 ± 71.1  0.34  1CON = no feed additive or hormone implant. 2MON = 33.1 mg/kg DM of monensin (Rumensin; Elanco, Greenfield, IN) and 12.2 mg/kg DM of tylosin phosphate (Tylan; Elanco, Greenfield, IN). 3IMP = 33.1 mg/kg DM of monensin, 12.2 mg/kg DM of tylosin phosphate, and implantation with a combination of 120 mg trenbolone acetate and 24 mg estradiol (Revalor-S; Intevet Inc., Millsboro, DE). 4BAA = 33.1 mg/kg DM of monensin, 12.2 mg/kg DM of tylosin phosphate, implantation with a combination of 120 mg trenbolone acetate and 24 mg estradiol, and supplemented with 8.3 mg/kg of DM of zilpaterol hydrochloride (Zilmax; Intervet Inc., Millsboro, DE). View Large Table 6. Average daily manure pH and reduction potential ± standard deviation by treatment   Treatment    Item  CON1  MON2  IMP3  BAA4  P-value  Manure pH  6.7 ± 0.4  6.7 ± 0.4  6.8 ± 0.6  6.7 ± 0.4  0.49  Manure redox potential, mV  95.3 ± 65.7  122.5 ± 50.5  131.7 ± 53.4  89.0 ± 71.1  0.34    Treatment    Item  CON1  MON2  IMP3  BAA4  P-value  Manure pH  6.7 ± 0.4  6.7 ± 0.4  6.8 ± 0.6  6.7 ± 0.4  0.49  Manure redox potential, mV  95.3 ± 65.7  122.5 ± 50.5  131.7 ± 53.4  89.0 ± 71.1  0.34  1CON = no feed additive or hormone implant. 2MON = 33.1 mg/kg DM of monensin (Rumensin; Elanco, Greenfield, IN) and 12.2 mg/kg DM of tylosin phosphate (Tylan; Elanco, Greenfield, IN). 3IMP = 33.1 mg/kg DM of monensin, 12.2 mg/kg DM of tylosin phosphate, and implantation with a combination of 120 mg trenbolone acetate and 24 mg estradiol (Revalor-S; Intevet Inc., Millsboro, DE). 4BAA = 33.1 mg/kg DM of monensin, 12.2 mg/kg DM of tylosin phosphate, implantation with a combination of 120 mg trenbolone acetate and 24 mg estradiol, and supplemented with 8.3 mg/kg of DM of zilpaterol hydrochloride (Zilmax; Intervet Inc., Millsboro, DE). View Large DISCUSSION The primary objective of this study was to determine the gaseous emission reduction potential per kilogram HCW from greater animal efficiency. Therefore, the study was designed to specifically evaluate GHG, VOC, and NH3 emissions from animals treated with growth promoting technologies during the last 20 d in the feeding period. Performance and carcass variables were analyzed to demonstrate that the treatment technologies resulted in expected performance and carcass trait differences typically observed in the literature. Increased performance due to growth promoting technologies was expected in the present study. In feedlot operations, improvements in cattle performance parameters such as ADG, feed intake, and feed efficiency from anabolic implantation supplementation maximizes resources and improves profitability (Wileman et al., 2009). Anabolic implantation had the most profound effect on growth in comparison to other treatments. We observed increased final BW by 48.3 kg and ADG by 0.45 kg/d in cattle treated with anabolic implants (IMP and BAA). In IMP and BAA treated cattle we observed a 7 and 9% increase in final BW and a 24 and 28% increase in ADG compared to CON and MON treated cattle, respectively. Our results are slightly higher than ADG improvements suggested in other studies, which range from 17 to 22% (Perry et al., 1991; Guiroy et al., 2002; Wileman et al., 2009). Implantation also resulted in greater feed efficiency. Wileman et al. (2009) reported a 9% or 0.2 kg increase in G:F from a meta-analysis comparing implanted versus nonimplanted cattle. There were no differences in ADG, final BW, or G:F observed between the IMP and BAA treatments in the present study. Vasconcelos et al. (2008) reported similar results from an experiment that used a similar anabolic implant strategy (trenbolone acetate plus estradiol-17β) to the present study. However, in an experiment that did not use an anabolic implant and in an experiment that used a progesterone plus estradiol benzoate implantation strategy, ZH treated cattle had greater ADG and final BW (Avendano-Reyes et al., 2006; Montgomery et al., 2009). The differences in ADG and final BW improvements observed in the literature may be a result of different anabolic implantation strategies with cattle implanted with estradiol-17β plus trenbolone acetate achieving higher ADG and final BW (Guiroy et al., 2002; Parr et al., 2011). Treatment with anabolic implant (IMP and BAA) resulted in the largest increase in HCW compared to CON and MON treated cattle. However, supplementation with the β-adrenergic agonist ZH increased HCW by 15.2 kg in comparison to IMP treated cattle. This is consistent with other studies where supplementation with ZH resulted in a 13 to 22 kg increase in HCW compared to cattle not treated with ZH (Avendano-Reyes et al., 2006; Elam et al., 2009; Montgomery et al., 2009; Parr et al., 2011). This increase in HCW is believed to be a result of the repartitioning of body mass from noncarcass components to carcass tissues or differences in tissue deposition rates for carcass and noncarcass components (Montgomery et al., 2009; Holland et al., 2010). Holland et al. (2010) suggested that ZH treated cattle have increased muscle mass due to greater deposition of consumed nutrients in muscle tissue. It has been well established that treatment with ZH results in greater dressing percent and LM area (Avendano-Reyes et al., 2006; Vasconcelos et al., 2008; Elam et al., 2009; Montgomery et al., 2009), which is consistent with the current study. Additionally, anabolic implantation increases LM area (Johnson et al., 1996; Bruns et al., 2005; Parr et al., 2011), which was observed in the present study. In contrast to experiments by Avendano-Reyes et al. (2006), Vasconcelos et al. (2008), Elam et al. (2009), and Montgomery et al. (2009), we did not observe differences in fat thickness, marbling score, KPH, yield grade, or quality grade in cattle treated with ZH. Parr et al. (2011) reported similar results to the present study, observing no difference in marbling score or quality grade distribution. The authors suspect this was due to the delayed harvest times of BW blocks due to emission measurement constraints and the heavier weights at which the animals were harvested, resulting in all cattle carrying more 12th rib fat than the industry average at market (1.27 cm). Methane (expressed in carbon dioxide equivalents) is the most abundant GHG that emanates from beef cattle production (USEPA, 2009). The primary source of CH4 is enteric fermentation where it is lost as a portion of gross energy intake (Johnson and Johnson, 1995). Comparatively, small amounts of CH4 are produced from anaerobic fermentation of manure deposited in corrals (Mosier et al., 1998); however, there are few studies that evaluate the contribution of the manure pack to GHG emissions. In the present study, CH4 emissions ranged from 0.61 to 0.73 g · kg HCW–1 · d–1. Treatment differences were observed with similar CH4 emissions emanating from the CON and IMP groups whereas treatment with MON and BAA reduced CH4 emissions by 8 and 15%, respectively. In a parallel experiment comparing natural and conventionally treated cattle, Cooprider et al. (2011) reported slightly higher CH4 results of 0.79 and 0.80 g · kg HCW–1 · d–1, respectively. However, no differences for anabolic implant, antibiotic, ionophore, or β-adrenergic agonist treatments were observed (Cooprider et al., 2011). The parallel experiment, conducted in the same University of California, Davis, CPE facilities used a different β-adrenergic agonist, ractopamine hydrochloride (Optaflexx; Elanco). This may explain the variation in treatment differences between the 2 experiments as ZH is reported to have a greater effect on performance variables and animal physiology (Avendano-Reyes et al., 2006). The authors would have expected a similar reduction in CH4 from the IMP and MON treated steers due to monensin's mechanism of reducing the levels of gram-positive bacteria that produce the majority of the substrates for methanogenesis. Further work may be warranted to better understand implantation and monensin interactions with CH4 emissions. The majority of experiments conducted on CH4 from cattle production have compared different treatment diets as diet manipulation has been found to have an effect on CH4 produced. McGeough et al. (2010a) studied the effects of corn silage harvest maturity on CH4 emissions, performance, and carcass characteristics from finished beef steers. Methane from feedlot steers fed corn silage at varying maturities ranged from 0.77 to 0.83 g · kg HCW–1 · d–1 whereas steers fed ad libitum concentrate diets emitted less CH4 emissions, averaged at 0.60 g · kg HCW–1 · d–1 (McGeough et al., 2010a). In a similar experiment comparing the effects of whole-crop wheat silages differing in grain content, McGeough et al. (2010b) observed CH4 emissions ranging from 0.71 to 0.85 g · kg HCW–1 · d–1 from cattle fed wheat silage. The authors also reported increased CH4 emissions from finishing steers fed a grass silage diet (0.84 g · kg HCW–1 · d–1) and decreased CH4 emissions from finishing steers fed an ad libitum concentrate diet of (0.44 g · kg HCW–1 · d–1). It is well documented that cattle fed high forage diets emit more CH4 than cattle fed high concentrate grain diets (McGinn et al., 2004; Beauchemin and McGinn, 2005; Jordan et al., 2006; Foley et al., 2009). Methane emission estimates from the current study fall well within the range of CH4 emissions reported from the previous experiments. However, the diet fed in the present study was most comparable to the ad libitum concentrate diets fed by McGeough et al. (2010a) where CH4 emissions were reported at 0.60 and 0.44 g · kg HCW–1 · d–1 for corn and wheat silage, respectively. These emissions demonstrate a broader range of CH4 emissions and are slightly lower than emissions from the present study, which is unexpected given the similarity in animal type and diet between the McGeough et al. (2010a) and the present study. The lower reported emissions by McGeough et al. (2010b) may be partially explained by use of the sulfur hexafluoride (SF6) tracer gas technique for emission measurement, which underestimates CH4 emissions by approximately 8% (Grainger et al., 2007) and does not account for CH4 from manure. Methane emissions are largely driven by DMI (Johnson and Johnson, 1995; Mills et al., 2003; Ellis et al., 2007) and may provide partial explanation for the increased CH4 emissions observed in the present study. Environmental chambers are considered to be the most accurate method for measuring gaseous emissions from livestock; however, animal behavior often changes during chamber housing, which can influence performance and DMI (Kebreab et al., 2006). Dry matter intake of beef cattle decreased during environmental chamber housing in 2 beef cattle experiments (Beauchemin and McGinn, 2005; Stackhouse et al., 2011). Beauchemin and McGinn (2005) reported CH4 emissions from a corn and barley finishing ration to be 0.28 and 0.39 g · kg HCW–1 · d–1, respectively. The authors reported a 22% decrease in DMI during chamber housing (Beauchemin and McGinn, 2005). Stackhouse et al. (2011) reported CH4 emission estimates from 540 kg Black Angus steers fed a similar diet to the present study to be 0.30 g · kg HCW–1 · d–1 and also reported a decrease in DMI due to chamber housing. In the previous experiments, cattle were not harvested on completion of the experiment so HCW was calculated using a dressing percent of 62.5%. Reported DMI from the previous studies were 14 to 33% less than the present study, which explains the increased CH4 emissions from cattle housed in the CPE. Furthermore, DMI did not decline in the present study when cattle were moved into the CPE. We suspect reductions in DMI were avoided by comfortable CPE housing that allowed animals to partake in normal behaviors and due to the larger group size (10 animals per group) in which the cattle were moved and housed. Nitrous oxide is primarily produced during the nitrification and denitrification processes of land applied manure (Jungbluth et al., 2001; Kebreab et al., 2006). Comparatively, small amounts of N2O are produced from manure deposited in corrals and even smaller quantities of N2O from enteric fermentation have been identified but not specifically quantified from beef and dairy cattle (Sun et al., 2008; Stackhouse et al., 2011). Kaspar and Tiedje (1981) suggested that N2O production is a few thousandths the rate of ammonium (NH4) formation occurring as a byproduct of dissimilatory nitrate reduction by rumen microbiota. In the present study, N2O ranged from 0.015 to 0.018 g · kg HCW–1 · d–1 and was 14% greater in the BAA versus other treatments. Our results are similar to a parallel experiment, conducted in the same University of California, Davis, CPE facilities, where N2O emission estimates were 0.013 and 0.016 g · kg HCW–1 · d–1 for natural and conventionally treated cattle, respectively (Cooprider et al., 2011). In an environmental chamber experiment where cattle were housed for 24 h, Stackhouse et al. (2011) reported that finished Black Angus steers emitted 0.0012 g · kg HCW–1 · d–1 (HCW calculated by 62.5% of the reported shrunk body weight). In comparison to this environmental chamber experiment, where similar animal types were used, N2O emissions from the present study were nearly an order of magnitude greater. However, Stackhouse et al. (2011) also reported 86% lower N2O emissions compared to an Australian feedlot experiment (Denmead et al., 2008), which used an inverse dispersion technique for emission measurement. There were no animal BW reported from the Australian study; therefore, a comparison in grams per kilogram HCW per day to the present study was impossible. Stackhouse et al. (2011) suggested that N2O emission estimates were low due to the environmental chambers concrete floor, which reduced denitrification and nitrification processes from the lack of denitrifiers normally present in soil. Furthermore, the authors suggested that N2O emissions observed from the environmental chamber may be from the digestive processes of the animal, as the animals only resided in the chamber for 24 h (Stackhouse et al., 2011). The present study is likely a more accurate representation of the net N2O emissions that come from feedlot animals housed on dirt corrals and likely represents N2O emissions from enteric fermentation and excreta emitted primarily during the nitrification of feed and manure nitrates. Ammonia emissions from the present study are difficult to compare to other NH3 emission estimates in the literature because other reported emission rates are from commercial feedlots using micrometeorological or inverse dispersion techniques. The majority of measured NH3 field emission data are reported from feedlots in semiarid climates. Measured NH3 emissions from Texas feedlots report daily emissions ranging from 85 to 150 g/animal (Flesch et al., 2007; Todd et al., 2008; Rhoades et al., 2010). Ammonia emissions are similar in the present study ranged from 0.19 to 0.33 g · kg HCW–1 · d–1 or 2.63 to 4.81 g · animal–1 · h–1 during the last 10 d of the feeding period and were lowest in the BAA treatment resulting in 30, 37, and 42% reduction compared to CON, MON, and IMP treated cattle, respectively. An in vivo experiment by Walker and Drouillard (2009) observed decreased ruminal NH3 concentrations in response to β-adrenergic agonist ractopamine hydrochloride treatment. The authors suggest that supplementation with ractopamine hydrochloride may impact rumen degradation of dietary protein. We suspect that supplementation with ZH may have a similar effect and is likely increasing protein deposition and decreasing turnover, ultimately reducing urea excretion and thus NH3 volatilization. In areas that are in nonattainment of federal and state ozone standards, such as the San Joaquin and Imperial Valleys of California, smog forming VOC emissions from animal agriculture are regulated. Ozone (smog) is formed through the interaction of VOC with nitrogen oxides (NOx) in the presence of sunlight and impairs human health and well-being as well as the regional and global environment. In California, feedlots are regulated based on dairy emission VOC factors due to the lack of information on VOC from beef operations. The 2 VOC that emanate from livestock production are MeOH and EtOH. It is believed that fresh excreta is 1 of the major sources of MeOH and EtOH (Miller and Varel, 2001; Filipy et al., 2006; Sun et al., 2008) and that EtOH accounts for 82 ± 10% of VOC from beef cattle (Howard et al., 2010). In the present study, EtOH and MeOH emissions ranged from 0.01 to 0.05 and 0.002 to 0.003 g · kg HCW–1 · d–1, respectively. Reductions in MeOH were observed from the BAA treated cattle. Ethanol emissions were lowest in the CON, IMP, and BAA treatments and were higher in the IMP and MON treated cattle. Very few experiments have measured MeOH and EtOH emissions from finished beef steers making comparisons with the literature impossible. In an environmental chamber experiment MeOH and EtOH were not reportable as gaseous concentrations were below the level of detection limit of the Innova 1412 (Stackhouse et al., 2011). In the present study, supplementation with ZH altered carbonaceous (CH4, EtOH, and MeOH) and nitrogenous (N2O and NH3) gas emissions from feedlot cattle. Beta-adrenergic agonists are fed to cattle the last 20 to 40 d before slaughter to increase muscle and reduce fat deposition (Mersman, 1998). Beta-adrenergic agonists are similar in chemical structure to the naturally occurring catecholamines dopamine, norepinephrine, and epinephrine (Bell et al., 1998). Supplementation with β-adrenergic agonists in ruminants results in stimulation of β-adrenergic receptors on cell surfaces, which increases skeletal muscle mass, cross-sectional area of individual muscles, or both (Chung and Johnson, 2008). The authors suspect that the lower NH3 emissions results from this increase in muscle mass and increased N requirements, resulting in less excreted urinary N. In an in vivo experiment using ractopamine hydrochloride supplementation on rumen fluid, Walker and Drouillard (2009) observed an increase in gas production, suggesting that ractopamine hydrochloride has an effect on rumen fermentation and microflora, potentially explaining changes in CH4 production observed in the present study. Furthermore, β-adrenergic receptors are found along the digestive tract and naturally occurring catecholamines affect gut motility and secretory response (Ruckebusch, 1983; McIntyre and Thompson, 1992), which may affect passage rate of ruminal fluid and particulate matter (Walker and Drouillard, 2009) and may explain the lower CH4 production from ZH treated animals. Naturally occurring catecholamines are also shown to increase the growth of gram negative bacteria (Lyte and Ernst, 1992; Kinney et al., 2000), which may affect starch and lactate fermentation as well as protein degradation that depend mostly on gram negative bacteria (Walker and Drouillard, 2009). In the present study, the authors did not measure the rumen environment but suspect that the observed treatment differences in carbonaceous emissions from ZH supplemented feedlot steers, which likely occurred due to the physiological responses in the rumen environment because emissions per animal were also lower. Greater animal performance is achieved by increasing animal efficiencies through improved nutrition, reproduction, genetics, and management (Boadi et al., 2004). In the beef industry, the use of growth promoting technologies such as growth implants, β-adrenergic agonists, antibiotics, and ionophores is prevalent in most feedlot operations to improve animal health, performance, and feed efficiency (Wileman et al., 2009). From an environmental sustainability perspective, improvements in animal productivity suggest that fewer inputs are required to produce the same product. In the present study, use of growth promoting technologies resulted in an additional 10% of product and supplementation with ZH reduced CH4, MeOH, and NH3 emissions compared to groups not treated with ZH. Future work is necessary to further understand the mechanism for emission reduction from the entire feeding period and to assess emissions from the full 20 d that ZH is fed to finishing beef cattle. The present study evaluated GHG, VOC, and NH3 abatement strategies for feedlots and provides additional validation data for models. 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TI - Growth promoting technologies reduce greenhouse gas, alcohol, and ammonia emissions from feedlot cattle
JF - Journal of Animal Science
DO - 10.2527/jas.2011-4885
DA - 2013-11-01
UR - https://www.deepdyve.com/lp/oxford-university-press/growth-promoting-technologies-reduce-greenhouse-gas-alcohol-and-bEqYPi7WO9
SP - 5438
EP - 5447
VL - 91
IS - 11
DP - DeepDyve
ER -