Non Technical Summary
Cattle release enteric methane (CH4) emissions out of their mouth that result from fermentation processes in their stomach (rumen). Capturing and measuring these emissions is of interest, because CH4 is a greenhouse gas and represents a loss of the potential energy in the feed the animal consumes. In this pilot study, we will use head boxes made of clear polycarbonate plastic, which the animal places its head in, to measure CH4 emissions from Holstein dairy heifers. An animal training and sampling protocol will be developed from this study for using the head box system in any future studies. Furthermore, there is little to no data on enteric CH4 emissions from grazing stocker cattle on native grass or wheat pastures in US production systems. A study will be conducted to quantify enteric CH4 emissions from cattle grazing dormant winter and early summer native range or winter wheat pasture and their subsequent individual finishing performance, feed efficiency, water intake, and enteric CH4 emissions. Heat stress in cattle is both an economic and animal well-being issue for the US beef industry. Annual US beef industry losses from heat stress are estimated to be $369 million and a large proportion of those losses occur in states such as Oklahoma that have large cattle populations and high summer temperatures (St-Pierre et al., 2003). Using shade structures in feedlot housing systems has been shown to improve animal performance (e.g. gain-to-feed ratio) and well-being (Mitloehner et al., 2001, Mitlohner et al., 2002, Gaughan et al., 2010), and has the potential to improve profitability, especially in areas that experience hot summers (e.g. the Southern Great Plains).The impacts of heat stress abatement strategies, such as shade, on feedlot economics and feed nitrogen use efficiency of the feedlot is an unexplored research topic. A study will be conducted to determine if shade use can simultaneously impact animal well-being, N use efficiency, and the economics of finishing beef cattle. The research will provide valuable insights to the cattle feeding industry on how a practical heat stress mitigation technique (i.e. shade) may simultaneously affect the well-being of cattle, the environmental impact of beef per unit of production, and feedlot economics. The proposed work will address the National Institute of Food and Agriculture's priority science area of Climate Change, and specifically address the challenges of mitigating and adapting to climate change and keeping American agriculture competitive while ending world hunger
Animal Health Component
Research Effort Categories
Goals / Objectives
1. Develop an animal training protocol for a ventilated head box system for enteric CH4 emission measurement. 2. Develop an animal sampling protocol for a ventilated head box system for enteric CH4 emission measurement in cattle. 3. Quantify enteric CH4 emissions from cattle grazing dormant winter and early summer native range or winter wheat pasture and their subsequent individual finishing performance, feed efficiency, water intake, and enteric CH4 emissions. 4. Evaluate the use of shade as a heat stress abatement strategy and its impact on animal well-being, performance, nitrogen use efficiency, and economics in feedlot steers.
1: 6 heifers between 14 and 18 mos. of age will be paired by body weight (BW) and used to assess the impact of being housed in a the ventilated head box system on feed intake and behavior, and determine intra- and inter-animal variability in CH4emissions from animals fed the same diet. In Ph. 1 (1wk), animals will be fed individually in pens that allow for visual and social contact with animals in neighboring pens. In Ph. 2 (1wk), each animal will be introduced to a metabolism stall with a head box attached for three 2 hour periods over the course of the week. Free choice feed and H2O will be available to the animals while in the head box, and they will be restrained by a head gate that will allow them to stand or lie down, but will limit their side-to-side and forward and backward mobility. For Ph. 3 (1wk), each animal will spend 6 consecutive hrs in the metabolism stall and head box for 3 x's over the course of the wk. For Ph. 4, each animal will be housed in the metabolism stall and head box for a 3d period. Animals will be feed individually in pens for another 21d (Ph. 5) after the initial 3d measurement period and then will be placed in the metabolism stall and head box for another 3d period (Ph. 6). Animals will be fed once per d and have access to free choice H2O during the entire measurement period. Rumination, respiration rate, and vocalization behavior will be monitored by live observation by trained observers in all phases. Accelerometers will be used throughout the study to determine the time each animal spends in the lying vs. standing position. Ambient temp. and RH will be monitored throughout the study. Hourly CH4and CO2emissions and O2consumption will be measured for the entire 3d period of Ph. 4 and 6 for each animal. Emission rates (ER) will be calculated by the following equation: E = (sum(Q) x (Cout-Cin))/n,where E is the gas emission rate from the head box (g/animal/hr),Coutis the average hourly mass concentration in the outlet air (g/m3),Cinis the mean hrly mass concentration in the ambient air (g/m3),Qis the ventilation rate at 20ºC and 1 ATM (m3/hr), andnis the number of total effective measurements. Daily ER for d1-3 of Ph.s 4 and 6 will be compared to determine the within animal day-to-day variation and animal-to-animal variation. ER of Ph. 4 and 6 will be compared to determine the repeatability of enteric CH4emissions of animals fed a consistent diet. Daily DMI will be recorded during all 6 phases and mean DMI from Ph. 1-3 and 5 will be compared to mean DMI in Ph. 4 and 6 to determine the impacts of the head boxes on feed intake. Lying vs. standing time, respiration rate, rumination behavior, and vocalization behavior will be compared for the non-gas measurement and gas measurement phases to determine the impact of the head box system on animal behavior.2:Once the 6 heifers in 1 have completed ph. 6, they will be fed for another 21d (Ph. 7) and then placed in the head boxes for another 3d measurement period (Ph. 8). Unlike the measurement periods in Ph. 4 and 6, where the animals are consuming anad libitumdiet, animals will be offered fed at a rate restricted to 2% of their BW on DM basis in ph. 8. This feed restriction strategy will be used to compare the inter- and intra-animal variability of CH4emissions during Ph. 6 compared to Ph. 8 to discern the impact of feed intake variability on CH4emissions. 3.40 cross-bred steers (~ initial BW of 240 kg) will be grazed in two consecutive years on either native range (NR) or winter wheat (WW) pasture (n = 20/yr) and will be finished at the WSBRC Insentec feeding barn. WW cattle will be on pasture from approximately Dec. to April, while NR will be grazed from approximately Dec. to Aug., depending on forage conditions. While on pasture, enteric CH4emissions will be measured for 3 two wk periods with a C-Lock GreenFeed system. Prior to the start date of either experiment, steers will be trained to use the system. Hand clipped samples of both NR and WW pastures will be collected throughout the grazing ph. and analyzed for nutrient content and digestibility. After the grazing period, steers will be housed in the Insentec feeding barn at the WSBRC and trained to use the automated feeders and waterers for determination of individual feed and H2O intake throughout the finishing period. Steers from both the NR and WW pastures will be trained to use the system in 1&2 to measure enteric CH4emissions. All cattle will be harvested at an average 1.27 cm BF thickness on the basis of their grazing treatment (NR or WW); thus, days on feed will not be the same for the two groups of cattle. All continuous data will be analyzed using Proc Mixed procedures in SAS to determine if there are significant differences between the 2 grazing treatments. Individual animals from NR and WW will be ranked by their average CH4emission rate during the grazing ph. and the finishing ph.. Ranks from the 2 ph.s will be compared using Spearman's rank correlations. Correlations between CH4emission rank and feed intake, feed efficiency (feed:gain), and H2O intake will be estimated. Daily CH4production across both ph.s per kg of HCW will be calculated to compare the enteric CH4emission intensity of the 2 grazing + finishing systems. 4:A total of 240 cross-bred steers with an approximate initial BW of 375 kg will be used in a 140d feeding study at the WSBRC at OSU. All steers will be blocked by BW and allocated in a randomized complete block design to 1 of 2 treatments, shade (SH) and no shade (NS). Shade structures will be constructed with an N-S orientation using 80% solar block shade cloth with the dimensions of 3.7 x 15.2 m to provide 3.7 m2of shade/steer. The shade structures will be placed in the center of the 12.2 x 30.5 m pens away from H2O and feed sources at a height of 6.1 m. The experimental unit will be the pen (15 steers/pen) with 8 reps/trt (n = 8) for all dependent variables with exception of H2O usage (n=4). Steers will be weighed on d 0, every 28 d throughout the trial, and prior to harvest. Free choice H2O will be available for all steers throughout the study and average H2O usage and peak demands will be determined with inline, digital-data-logging H2O flow meters. Feed N intake will be calculated with the following equation: Feed N intake (g/steer/d) = [feed N offered daily (kg/dfeedx %DMfeedx % Nfeed) - orts N (kg/dortsx % DMortsx % Norts) x 1000 g/kg]/number of steers per pen. Retained N, protein retention, and excreted N will be calculated using equations in the 2000 Beef NRC. Efficiency of feed N use will be calculated as: Retained N (g/steer/d)/ Feed N intake (g/steer/d). Gaseous N losses will be estimated by using the following equation from Cole et al. (2006):N volatilization (% of N intake) = [N:P of diet - N:P of manure]/N:P of the diet. Total N and P analysis of the feed will be used to determine N:P of the diet and air dried manure samples collected from the concrete apron in the pen on the last day on feeding will be analyzed to determine the N:P of manure. Ambient and pen environmental temp., RH, solar radiation, black globe temp., and wind speed will be continuously recorded. All cattle will be harvested at an average 1.27 cm BF thickness on an individual pen basis. At harvest, HCW, KPH fat percentage, 12thrib BF, marbling score, USDA Quality and Yield Grade will be collected. To calculate the economic impacts of shade use, construction and maintenance costs of shade, feed costs, vet./med. costs, labor and management costs, and purchase and selling prices of the cattle will be used to calculate the impact of shade on total cost of gain (over the 140 d feeding period) and cost-per-kg of gain. If shade favorably impacts the cost of gain, a payback period analysis will be conducted for the shade construction and maintenance costs.All continuous data will be analyzed using Proc Mixed procedures in SAS to determine if there are significant differences between treatments.