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Methane emissions from growing dairy heifers estimated using an automated head chamber (GreenFeed) compared to respiration chambers or SF6 techniques
... Huhtanen et al. (2013a) found that between-animal variability was similar or slightly greater with the GreenFeed measurements compared with chamber studies. Hammond et al. (2013) reported a non-significant difference between mean CH 4 production from heifers when CH 4 production was measured by the GreenFeed device and by respiration chamber (215 and 198 g/d, respectively). ...
... In the same study, values obtained using the GreenFeed method were not comparable with those from the SF 6 method. The authors attributed this to a lower number of visits to GreenFeed during grazing measurements (Hammond et al., 2013). An advantage of the methods described by Madsen et al. (2010) and Garnsworthy et al. (2012) and the GreenFeed method is that a large number of animals in their natural environment can be measured with relatively low investment and labour costs. ...
... g/d) with Holstein heifers fed alfalfa silage. Hammond et al. (2013;201.8 g/d) reported that dairy heifers grazing pasture in Reading, UK, had greater CH 4 emissions (g/d; 34%) than in our experiment, whether measured in the AHCS or in respiration chambers. ...
... A concern with the spot-measuring technique expressed by some researchers (Hegarty, 2013;Hammond et al., 2016;Waghorn et al., 2016) has been the large diurnal variation noted in CH 4 emission rates associated with meal-fed ruminants (Kinsman et al., 1995;Robinson et al., 2015;Jonker et al., 2016). However, with cattle grazing pasture, these diurnal patterns have been found not to be as distinct as with meal-fed cattle (Hammond et al., 2013;Gunter and Bradford, 2015). Because grazing cattle have a constant feed source, they would likely require fewer spot samples to achieve a precise estimate when compared with meal-fed animals. ...
Agricultural methane (CH4) emissions worldwide account for approximately 43% of all anthropogenic CH4 emissions, and the majority of agricultural CH4 emissions are attributed to enteric fermentation within ruminant livestock. Therefore, interest is heightened in quantifying and mitigating this source. The automated head-chamber system (AHCS; GreenFeed, C-Lock Inc., Rapid City, SD) evaluated here can be placed in a pasture with grazing cattle to measure their CH4 and CO2 emissions and O2 consumption. However, improper management of an AHCS might have a significant effect on gas exchange estimates. One factor that may affect the quality of these estimates is the rate that bait is delivered and the length of time an animal has its muzzle in front of the intake manifold for sampling. During both experiments, at each visit to the AHCS an electronic ear tag triggered the delivery of 6-mm alfalfa pellets (bait; 32-g increments) at timed intervals up to 8 times per visit and a maximum of 4 sampling events/d. In Exp. 1, the AHCS was programmed to deliver feed at 18- (n = 2), 21- (n = 4), 24- (n = 4), or 27-s (n = 3) intervals for 73 d; in Exp. 2 the AHCS was programmed to deliver feed at 19- (n = 2), 27- (n = 4), 35- (n = 4), or 43-s (n = 3) intervals for 43 d. The AHCS was programmed to measure CH4, CO2, and O2 (Exp. 2 only) fluxes at each visit during the experiments. Time intervals were analyzed by ANOVA, and least squares means were compared using linear and quadratic contrasts. Carbon dioxide emission estimates were not affected by time interval in either experiment. Methane emission estimates and the ratio of CH4:CO2 linearly decreased (P < 0.01) with increasing time increment in Exp. 1 but was not different in Exp. 2. Time increment did not affect the O2 consumption estimate in Exp. 2. Increasing the time increment increased (P < 0.01) the time cattle spent in the AHCS but did not affect the amount of bait consumed. Cattle did not respond consistently to increasing time increment for bait delivery, and bait delivery interval had minimal effect on gas emission and consumption estimates.
... Feeding steers with a Calan gate system allowed steers to maintain pen dynamics and still allowed individual feed intake measurements. With validation of the GF (Hammond et al., 2013;Waghorn et al., 2013;Huhtanen et al., 2013), CO 2 and CH 4 were able to be determined. Consequently, heat production was determined using the equation of Brouwer (1965) assuming a respiratory quotient of 1.05. ...
... Cattle were still able to have pen interactions, and the current model theoretically accounted for the pen environment. Also, the current model used a less in-vasive procedure such as the sulfur hexafluoride (SF6) procedure (Hammond et al., 2013) to measure CO 2 and CH 4 . However, this model does come with limitations. ...
Condensed tannins (CT) may decrease greenhouse gas emissions and alter the site of N excreted by ruminants. We evaluated the effect of top-dressing a steam-flaked corn–based finishing diet (14.4% CP and NEg 1.47 Mcal/kg) for beef cattle with a commercially available CT extract at 3 levels (0, 0.5, and 1.0% of diet, DM basis). Angus-crossbred steers (n = 27; 350 ± 32 kg initial BW) were individually fed via Calan gates for 126 d. Diet digestibility and N balance were estimated after 34 and 95 d on feed (Phase 1 and Phase 2, respectively) using titanium dioxide as a marker of fecal output and the creatinine:BW ratio as a marker for urine output. Ruminal CH4 and metabolic CO2 fluxes were measured using a GreenFeed system (C-Lock Inc., Rapid City, SD) for 2 sampling periods that coincided with fecal and urine sampling. Urine energy loss was estimated from urine N excretion, assuming all excreted N was urea. Oxygen consumption was estimated from CO2 production assuming a respiratory quotient of 1.05. Average daily gain (2.08, 2.14, and 2.08 kg/d for 0, 0.5, and 1.0% CT, respectively) and G:F did not differ (P = 0.88) among treatments. Starch intake and OM intake did not differ (P ≥ 0.42) among treatments during each phase. Apparent total tract starch digestibility during Phase 1 linearly decreased (P = 0.04) with inclusion of CT. Apparent total tract digestibility of OM and starch were not different among treatments (P ≥ 0.13) during Phase 2. Nitrogen intake did not differ (P ≥ 0.16) among treatments during each phase, but fecal N excretion linearly increased (P = 0.05) with inclusion of CT during Phase 1. Urinary N excretion was not different (P ≥ 0.39) among treatments during both phases, but urinary N as a proportion of total N excretion linearly decreased (P = 0.01) when CT was included in the diet during Phase 1. Retained N was not different (P ≥ 0.27) among treatments during each phase. Fluxes of CO2 were similar (P ≥ 0.37) among treatments during both phases. No differences (P ≥ 0.23) were observed for percentage of GE intake lost as CH4 (2.99, 3.12, and 3.09% in Phase 1 and 3.54, 3.55, and 4.35% in Phase 2) for 0, 0.5, and 1.0% CT, respectively. No difference (P ≥ 0.42) was observed for heat production lost as a percent of GE intake during both phases. Growth performance, gas emissions, and energetic losses were not affected by the inclusion CT in a steam-flaked corn–based finishing diet. © 2017 American Society of Animal Science. All rights reserved.
... This allows test animals to express normal grazing behavior, including diet selection over the forages confi ned within the polytunnel space (Table 5.1 ). They have been used in the UK to measure ( 2012 ), Hammond et al. ( 2013 ) Requires the use of a feed "attractant" to lure the animal to the facility, which alters results ...
... Greenfeed ® is a patented device (Zimmerman and Zimmerman 2012 ) that measures and records short-term (3-6 min) CH 4 emissions from individual cattle repeatedly over 24 h by attracting animals to the unit using a "bait" of pelleted concentrate. By being available 24 h day −1 potential sampling bias is reduced and the technique has been shown to provide comparable estimates to those produced both by respiratory chamber and SF 6 techniques (Hammond et al. 2013 ). However, a signifi cant limitation of the technique is the requirement to supply an "attractant" to lure the animal to use the facility, consisting of up to 1 kg of concentrate pellets per day. ...
This book provides standards and guidelines for quantifying greenhouse gas emissions and removals in smallholder agricultural systems and comparing options for climate change mitigation based on emission reductions and livelihood trade-offs. Globally, agriculture is directly responsible for about 11% of annual greenhouse gas (GHG) emissions and induces an additional 17% through land use change, mostly in developing countries. Farms in the developing countries of sub-Saharan Africa and Asia are predominately managed by smallholders, with 80% of land holdings smaller than ten hectares. However, little to no information exists on greenhouse gas emissions and mitigation potentials in smallholder agriculture. Greenhouse gas measurements in agriculture are expensive, time consuming, and error prone, challenges only exacerbated by the heterogeneity of smallholder systems and landscapes. Concerns over methodological rigor, measurement costs, and the diversity of approaches, coupled with the demand for robust information suggest it is germane for the scientific community to establish standards of measurements for quantifying GHG emissions from smallholder agriculture. Standard guidelines for use by scientists, development organizations will help generate reliable data on emissions baselines and allow rigorous comparisons of mitigation options. The guidelines described in this book, developed by the CGIAR Research Program on Climate Change, Agriculture, and Food Security (CCAFS) and partners, are intended to inform anyone conducting field measurements of agricultural greenhouse gas sources and sinks, especially to develop IPCC Tier 2 emission factors or to compare mitigation options in smallholder systems.
... This allows test animals to express normal grazing behavior, including diet selection over the forages confi ned within the polytunnel space (Table 5.1 ). They have been used in the UK to measure ( 2012 ), Hammond et al. ( 2013 ) Requires the use of a feed "attractant" to lure the animal to the facility, which alters results ...
... Greenfeed ® is a patented device (Zimmerman and Zimmerman 2012 ) that measures and records short-term (3-6 min) CH 4 emissions from individual cattle repeatedly over 24 h by attracting animals to the unit using a "bait" of pelleted concentrate. By being available 24 h day −1 potential sampling bias is reduced and the technique has been shown to provide comparable estimates to those produced both by respiratory chamber and SF 6 techniques (Hammond et al. 2013 ). However, a signifi cant limitation of the technique is the requirement to supply an "attractant" to lure the animal to use the facility, consisting of up to 1 kg of concentrate pellets per day. ...
Accurate measurement techniques are needed for determining greenhouse gas (GHG) emissions in order to improve GHG accounting estimates to IPCC Tiers 2 and 3 and enable the generation of carbon credits. Methane emissions from agriculture must be well defined, especially for ruminant production systems where national livestock inventories are generated. This review compares measurement techniques for determining methane production at different scales, ranging from in vitro studies to individual animal or herd measurements. Feed intake is a key driver of enteric methane production (EMP) and measurement of EMP in smallholder production systems face many challenges, including marked heterogeneity in systems and feed base, as well as strong seasonality in feed supply and quality in many areas of sub-Saharan Africa.
In vitro gas production studies provide a starting point for research into mitigation strategies, which can be further examined in respiration chambers or ventilated hood systems. For making measurements under natural grazing conditions, methods include the polytunnel, sulfur hexafluoride (SF6), and open-path laser. Developing methodologies are briefly described: these include blood methane concentration, infrared thermography, pH, and redox balance measurements, methanogen population estimations, and indwelling rumen sensors.
... The GQS measured spot QCO 2 and QCH 4 with less variability than a nonflux spot sampling of emitted carbon in lactating dairy cows (Huhtanen et al., 2015). Compared with calorimetric chambers, the GQS yielded similar results of emitted carbon (Hammond et al., 2013). The objective of the current study was to use the GQS technique as a proof-of-concept methodology to estimate DMI and differences in intake levels in lactating dairy cows fed for ad libitum (AL) or restricted intake (RI). ...
... For instance, the spot measurements standard deviation and coefficient of variation for QCO 2 were 1,176 L/d and 8.72%, respectively (measured using individual 5-min spot measurements of all cows). Variation in spot short-term measurements of carbon gases may be reduced by increasing sampling frequency and using the GQS for longer periods, as hypothesized by Hammond et al. (2013) and Dorich et al. (2015). The coefficient of Probability of treatment effect (AL vs. RI); significance was declared at P ≤ 0.05 and trends at 0.05 < P ≤ 0.10. ...
The objective of this study was to use spot short-term measurements of CH4 (QCH4) and CO2 (QCO2) integrated with backward dietary energy partition calculations to estimate dry matter intake (DMI) in lactating dairy cows. Twelve multiparous cows averaging 173 ± 37 d in milk and 4 primiparous cows averaging 179 ± 27 d in milk were blocked by days in milk, parity, and DMI (as a percentage of body weight) and, within each block, randomly assigned to 1 of 2 treatments: ad libitum intake (AL) or restricted intake (RI = 90% DMI) according to a crossover design. Each experimental period lasted 22 d with 14 d for treatments adaptation and 8 d for data and sample collection. Diets contained (dry matter basis): 40% corn silage, 12% grass-legume haylage, and 48% concentrate. Spot short-term gas measurements were taken in 5-min sampling periods from 15 cows (1 cow refused sampling) using a portable, automated, open-circuit gas quantification system (GreenFeed, C-Lock Inc., Rapid City, SD) with intervals of 12 h between the 2 daily samples. Sampling points were advanced 2 h from a day to the next to yield 16 gas samples per cow over 8 d to account for diurnal variation in QCH4 and QCO2. The following equations were used sequentially to estimate DMI: (1) heat production (MJ/d) = (4.96 + 16.07 ÷ respiratory quotient) × QCO2; respiratory quotient = 0.95; (2) metabolizable energy intake (MJ/d) = (heat production + milk energy) ± tissue energy balance; (3) digestible energy (DE) intake (MJ/d) = metabolizable energy + CH4 energy + urinary energy; (4) gross energy (GE) intake (MJ/d) = DE + [(DE ÷ in vitro true dry matter digestibility) - DE]; and (5) DMI (kg/d) = GE intake estimated ÷ diet GE concentration. Data were analyzed using the MIXED procedure of SAS (SAS Institute Inc., Cary, NC) and Fit Model procedure in JMP (α = 0.05; SAS Institute Inc.). Cows significantly differed in DMI measured (23.8 vs. 22.4 kg/d for AL and RI, respectively). Dry matter intake estimated using QCH4 and QCO2 coupled with dietary backward energy partition calculations (Equations 1 to 5 above) was highest in cows fed for AL (22.5 vs. 20.2 kg/d). The resulting R(2) were 0.28 between DMI measured and DMI estimated by gaseous measurements, and 0.36 between DMI measured and DMI predicted by the National Research Council model (2001). Results showed that spot short-term measurements of QCH4 and QCO2 coupled with dietary backward estimations of energy partition underestimated DMI by 7.8%. However, the approach proposed herein was able to significantly discriminate differences in DMI between cows fed for AL or RI.
... Major shortcomings of AHCS include unrepresentative sampling (in applications, such as grazing systems, where the animals have to voluntarily visit the unit) and the use of bait feed, which could represent up to 5% of the animal's dry matter intake during a gas measurement event. Recent comparative experiments have concluded that AHCS produces emission rates comparable to those estimated using respiration chambers or the SF 6 technique 9,10 . The stand-alone AHCS system is constructed around a robust automatic feeder that is easily transportable by hand or can be mounted to a trailer equipped with solar panels (or other power sources) for autonomous field operation and long distance travel. ...
... Comparative tests with AHCS vs. established CH 4 measurement techniques support the above conclusions. For example, a study with growing dairy heifers concluded that AHCS was capable of estimating CH 4 emissions from livestock and emission estimates generated by AHCS were comparable to values obtained by respiration chambers 9 . These authors pointed out that deployment of the AHCS units and replication must be carefully considered to ensure sufficient numbers of measurements are obtained. ...
Ruminant animals (domesticated or wild) emit methane (CH4) through enteric fermentation in their digestive tract and from decomposition of manure during storage. These processes are the major sources of greenhouse gas (GHG) emissions from animal production systems. Techniques for measuring enteric CH4 vary from direct measurements (respiration chambers, which are highly accurate, but with limited applicability) to various indirect methods (sniffers, laser technology, which are practical, but with variable accuracy). The sulfur hexafluoride (SF6) tracer gas method is commonly used to measure enteric CH4 production by animal scientists and more recently, application of an Automated Head-Chamber System (AHCS) (GreenFeed, C-Lock, Inc., Rapid City, SD), which is the focus of this experiment, has been growing. AHCS is an automated system to monitor CH4 and carbon dioxide (CO2) mass fluxes from the breath of ruminant animals. In a typical AHCS operation, small quantities of baiting feed are dispensed to individual animals to lure them to AHCS multiple times daily. As the animal visits AHCS, a fan system pulls air past the animal’s muzzle into an intake manifold, and through an air collection pipe where continuous airflow rates are measured. A sub-sample of air is pumped out of the pipe into non-dispersive infra-red sensors for continuous measurement of CH4 and CO2 concentrations Field comparisons of AHCS to respiration chambers or SF6 have demonstrated that AHCS produces repeatable and accurate CH4 emission results, provided that animal visits to AHCS are sufficient so emission estimates are representative of the diurnal rhythm of rumen gas production. Here, we demonstrate the use of AHCS to measure CO2 and CH4 fluxes from dairy cows given a control diet or a diet supplemented with technical-grade cashew nut shell liquid.
Open access at:
http://www.jove.com/video/52904/the-use-an-automated-system-greenfeed-to-monitor-enteric-methane
... The commercially produced GreenFeed emission monitoring system (GEM; C-Lock Inc., Rapid City, SD, USA) measures flux directly over periods of~5 min as cattle access a bait station at programmed intervals when these emissions are measured (Zimmerman et al. 2013). Initial validation studies of the GEM have shown DMP estimates correlate highly with open circuit calorimetry measures in which all emissions throughout the day are measured (Hammond et al. 2013), so the GEM system was selected to quantify mitigation of DMP by dietary nitrate in feedlot cattle. This study was conducted to verify that nitrate salts could be safely included in the TMR of feedlot cattle and would reduce the DMP and methane yield (g CH 4 /kg dry matter intake (DMI)) as expected from published literature. ...
... The measured mitigation was less than expected based on measured DMI and calculated rumen stoichiometry, which could reflect either emissions not being as predicted or inaccuracy in the estimation of DMP. Because this short-term emission measurement system (GEM) has had its emission estimates correlated with respiration chambers (Hammond et al. 2013), we have little reason to doubt measurement accuracy. However, the significant diet effect on the interval between feed consumption and methane measurement identifies the need for caution in extrapolating short-term emission measures into daily emission rates when quick-acting rumen modifiers such as nitrate are being evaluated. ...
Nitrate may serve as a non-protein nitrogen (NPN) source in ruminant diets while also reducing enteric methane emissions. A study was undertaken to quantify methane emissions of cattle when nitrate replaced urea in a high concentrate diet. Twenty Angus steers were allocated to two treatment groups and acclimated to one of two iso-energetic and iso-nitrogenous finisher rations (containing NPN as urea or as calcium nitrate), with all individual feeding events recorded. A single methane measurement device (C-lock Inc., Rapid City, SD, USA) was exchanged weekly between treatments (2 1-week periods per treatment) to provide estimations of daily methane production (DMP; gCH(4)/day). A 17% reduction in estimated DMP (P = 0.071) resulted from nitrate feeding, attributed to both a tendency for reduced dry matter intake (DMI; P = 0.088) and H-2 capture by the consumed nitrate. NO3-fed cattle consumed a larger number of meals (14.69 vs 7.39 meals/day; P < 0.05) of smaller size (0.770 vs 1.820 kg/meal) each day, so the average interval between a feeding event and methane measurement was less in NO3-fed cattle (3.44 vs 5.15 h; P < 0.05). This difference could potentially have skewed the estimated DMP and contributed to the tendency (P = 0.06) for NO3-fed cattle to have a higher methane yield (gCH(4)/kg DMI) than urea-fed cattle. This study found short-term methane emission measurements made over 2 weeks (per treatment group) were adequate to show dietary nitrate tended to reduce emission and change the feeding pattern of feedlot cattle. Changes in feeding frequency may have confounded the ability of short-term methane measurements to provide data suitable for accurately estimating methane per unit feed intake.
... where Cp(i) is the fractional capture rate of air at time i; [CH 4 ]c(i) and [CH 4 ]b(i) are the concentrations of captured gas (ppm) and background gas of CH 4 (ppm), respectively, at time i; and Fair(i) is the volumetric airflow rate (L/min) measured on a dry-gas basis at time i. [26,33]. The system provides comparable estimates to those produced both by RC and SF 6 techniques [24,57]. The measurements with sufficient duration (at least 3 min), and 30 observations were enough to obtain reliable CH 4 emission data, regardless of how many times per day the measurements were obtained [37,58]. ...
This review aims to elucidate the contemporary methods of measuring and estimating methane (CH4) emissions from ruminants. Six categories of methods for measuring and estimating CH4 emissions from ruminants are discussed. The widely used methods in most CH4 abatement experiments comprise the gold standard respiration chamber, in vitro incubation, and the sulfur hexafluoride (SF6) techniques. In the spot sampling methods, the paper discusses the sniffer method, the GreenFeed system, the face mask method, and the portable accumulation chamber. The spot sampling relies on the measurement of short-term breath data adequately on spot. The mathematical modeling methods focus on predicting CH4 emissions from ruminants without undertaking extensive and costly experiments. For instance, the Intergovernmental Panel on Climate Change (IPCC) provides default values for regional emission factors and other parameters using three levels of estimation (Tier 1, 2 and 3 levels), with Tier 1 and Tier 3 being the simplest and most complex methods, respectively. The laser technologies include the open-path laser technique and the laser CH4 detector. They use the laser CH4 detector and wireless sensor networks to measure CH4 flux. The micrometeorological methods rely on measurements of meteorological data in line with CH4 concentration. The last category of methods for measuring and estimating CH4 emissions in this paper is the emerging technologies. They include the blood CH4 concentration tracer, infrared thermography, intraruminal telemetry, the eddy covariance (EC) technique, carbon dioxide as a tracer gas, and polytunnel. The emerging technologies are essential for the future development of effective quantification of CH4 emissions from ruminants. In general, adequate knowledge of CH4 emission measurement methods is important for planning, implementing, interpreting, and comparing experimental results.
... Greenfeed ® is a patented device (Zimmerman and Zimmerman, 2012) that measures and records short-term (3-6 min duration) CH 4 emissions from individual cattle repeatedly over 24 h by attracting animals to the unit using a "bait" of pelleted concentrate. By being available 24 h/day, potential sampling bias is reduced, and the technique has been shown to provide comparable estimates to that produced by both respiratory chamber and SF 6 techniques (Hammond et al. 2013). However, a significant limitation of the technique is the requirement to supply an "attractant" to lure the animal to use the facility, consisting of up to 1 kg of concentrate pellets per day. ...
Agriculture is a significant source of GHGsglobally and ruminant livestock animals are one of the largest contributors to these emissions, responsible for an estimated 14% of GHGs (CH 4 and N 2 O combined) worldwide. A large portion of GHG fluxes from agricultural activities is related to CH 4 emissions from ruminants. Both direct and indirect methods are available. Direct methods include enclosure techniques, artificial (e.g. SF 6 ) or natural (e.g. CO 2 ) tracer techniques, and micrometeorological methods using open-path lasers. Under the indirect methods, emission mechanisms are understood, where the CH 4 emission potential is estimated based on the substrate characteristics and the digestibility (i.e. from volatile fatty acids). These approximate methods are useful if no direct measurement is possible. The different systems used to quantify these emission potentials are presented in this chapter. Also, CH 4 from animal waste (slurry, urine, dung) is an important source: methods pertaining to measuring GHG potential from these sources are included.
... Analysis for a circadian variation in the instantaneous production rates of CO 2 and CH 4 within these data showed that the instantaneous production of CO 2 and CH 4 ranged from a low of 117 and 12 L/h, respectively, during the late morning (0600 to 1159 h), to a high of 129 and 14 L/h, respectively, in the evening (1800 to 2359 h); only a 16% increase. Hence, CO 2 and CH 4 emissions from grazing cattle were affected by a circadian emission pattern, but the variation was much less pronounced than with meal fed cattle (Hammond et al., 2013;Gunter and Bradford, 2015). Hence, with grazing cattle, the range in hourly CO 2 and CH 4 emission rates during the day is greatly reduced compared to meal-fed cattle, so the use of 'snapshot' sampling to estimate daily CO 2 and CH 4 emissions probably gives an accurate estimate when animals have ad libitum feed available and sampling is distributed throughout the day. ...
Ruminants are a source of enteric CH4, which has been identified as an anthropogenic greenhouse gas that contributes to climate change. With interest in developing technologies to decrease enteric CH4 emissions, systems are currently being developed to measure CH4 emissions by cattle. An issue with grazing cattle is the ability to measure CH4 emissions in open-air environments. A scientific instrument for this task is an automated, open-circuit gas quantification system (GQS; C-Lock, Inc.; Rapid City, SD). The GQS is a head-chamber that grazing cattle occasionally visit (3 to 8 min/visit; 3 to 6 visits/d) and, while the animal consumes a small portion of bait (0.5 to 1.0 kg/visit), the GQS captures the animal’s breath cloud by exhausting air through the GQS. The breath cloud is then analyzed for CH4, CO2, and O2 concentrations. Data are hourly uploaded to a server where it is processed using algorithms to determine total daily fluxes. Several factors affect emission estimates generated by the GQS including the animal’s visitation rate, length of sampling period, and airflow through the system. The location of the GQS is an important factor in determining the cattle’s willingness to visit. Further, cattle need to be trained to use the GQS, which normally requires 4 to 8 wk. Several researchers have shown that 30 or more visits are required to obtained high-quality estimates of gas fluxes. Once cattle are trained to use the GQS, the bait delivery rate has little effect on the animal’s willingness to use the system. Airflow through the GQS is an important factor, but as long as airflow is maintained above 26 L/s the breath-cloud capture seems nearly complete. There is great concern regarding circadian variation in the instantaneous production rates of CH4 because the GQS normally only spot-samples 2 to 4 times/d. Preliminary analysis has shown variation in the instantaneous production rates of CH4 do not vary as greatly with grazing cattle compared to meal-fed cattle. It seems that increasing the visitation length decreases variation in estimated emissions, but there is a diminishing return to increasing visitation length. The GQS is a useful tool for researching the nutrition and emissions of grazing cattle, but great care must be taken to obtain the best quality data possible for use in this high-impact research.
... (South Dakota, USA) to measure methane emissions from cattle in livestock buildings and out at pasture by limiting human intervention that might change the animal's behavior (Zimmerman et al., 2013a;Zimmerman et al., 2013b;Zimmerman et al., 2011). This system was developed as an alternative to the indirect method using SF 6 tracer gas (Application note 18) which was more difficult to implement (Hammond et al., 2013). More recently, C-Lock has also adapted the system to measure methane emissions from sheep. ...
Air pollutant and greenhouse gas emissions have recently become an environmental
concern for livestock farmers. In France, livestock farming plays a major contribution to air
pollutant emissions, amounting to over 70% of national ammonia (NH3) emissions and 75%
of methane (CH4) emissions. Currently, the measurement of emissions from livestock is still
not very widespread, limiting the number of references available for national livestock
production that can be used to guide farmers on how to modify their production systems to
reduce emissions. This review was drawn up by the ADEME and the RMT “Livestock and
Environment” to set out the main measurement methods used to quantify greenhouse gas,
ammonia and nitrous oxide (dinitrogen monoxide) emissions from livestock production
systems. The main aim is to provide the information required to help potential users
determine which quantification methods are most suitable for their requirements and how
much the equipment is likely to cost.
... The agreement in DMP determined by GEM and RC techniques together with the low SE of fitted values for DMP and MY in this study, demonstrates that the GEM unit is sufficiently accurate to be used for emission quantification. This is consistent with other recent comparisons (Hammond et al., 2013;Hegarty, 2013;Huhtanen et al., 2013) where a high level of agreement between GEM and other methods were observed (differences less than 8%, P > 0.10). Huhtanen et al. (2013) Eructation events appear as a sharp peak in solid line, being less frequent and less regular from cattle when they attend the GEM water unit. ...
Methods to measure enteric methane (CH4) emissions from individual ruminants in their production environment are required to validate emission inventories and verify mitigation claims. Estimates of daily methane production (DMP) based on consolidated short-term emission measurements are developing, but method verification is required. Two cattle experiments were undertaken to test the hypothesis that DMP estimated by averaging multiple short-term breath measures of methane emission rate did not differ from DMP measured in respiration chambers (RC). Short-term emission rates were obtained from a GreenFeed Emissions Monitoring (GEM) unit, which measured emission rate while cattle consumed a dispensed supplement. In experiment 1 (Expt. 1), four non-lactating cattle (LW=518 kg) were adapted for 18 days then measured for six consecutive periods. Each period consisted of 2 days of ad libitum intake and GEM emission measurement followed by 1 day in the RC. A prototype GEM unit releasing water as an attractant (GEM water) was also evaluated in Expt. 1. Experiment 2 (Expt. 2) was a larger study based on similar design with 10 cattle (LW=365 kg), adapted for 21 days and GEM measurement was extended to 3 days in each of the six periods. In Expt. 1, there was no difference in DMP estimated by the GEM unit relative to the RC (209.7 v. 215.1 g CH4/day) and no difference between these methods in methane yield (MY, 22.7 v. 23.7 g CH4/kg of dry matter intake, DMI). In Expt. 2, the correlation between GEM and RC measures of DMP and MY were assessed using 95% confidence intervals, with no difference in DMP or MY between methods and high correlations between GEM and RC measures for DMP (r=0.85; 215 v. 198 g CH4/day SEM=3.0) and for MY (r=0.60; 23.8 v. 22.1 g CH4/kg DMI SEM=0.42). When data from both experiments was combined neither DMP nor MY differed between GEM- and RC-based measures (P>0.05). GEM water-based estimates of DMP and MY were lower than RC and GEM (P
... All variables were logged at 1-s intervals. The system was recently validated by Hammond et al. (2013) against equivalent gas measurements conducted on respiration chambers, or by the use of the sulfur-hexafluoride (SF 6 ) tracer technique. A more complete description and operation of the equipment at the PDRC and calculation of gas fluxes is provided in Huhtanen et al. (2015). ...
Proper performance monitoring of cows on pasture-based diets is crucial to inform nutritional recommendations that minimize undesirable effects of high ruminant CH4 emissions into the environment. The prediction of linkages between rumination patterns, methane emissions, and correlated production traits of cows in a pasture-based automatic milking system was tested. A previous 10-d baseline measurement of rumination activity by acoustic methodology of 156 Holstein-Friesian cows was used for frequency analysis of rumination time and identification of 2 treatment groups (n = 37 cows/group) represented by cows with consistently high (HR; 75th rumination percentile = 617.55 ± 81.37 min/d) or low (LR; 25th rumination percentile = 356.65 ± 72.67 min/d) rumination. The HR and LR cows were paired by nearest parity, days in milk, body weight (BW), and previous 10-d milk production, and within pairs randomly assigned to 1 of 2 experimental groups managed on a voluntary milking system with diets consisting of at least 75% pasture, plus concentrates. Animal traits, including rumination time, mass flux of CH4 (QCH4) and carbon dioxide (QCO2), milk production, and estimated dry matter intake according to individual QCO2 fluxes over a 22-d period were analyzed with repeated measure mixed models for a completely randomized design, structural equation modeling, and nonlinear regression. High rumination and methane was seen in older and heavier cows that had greater estimated dry matter intake and milk production. A consistent difference in rumination time and QCH4 across days was detected between HR and LR, even after adjustment for metabolic BW. Estimated dry matter intake had direct positive effects on rumination and QCH4, but no independent direct effect of rumination on QCH4 was detected. The LR cows produced more QCH4/milk, associated with lower milk, BW, concentrate intake, and greater activity at pasture. A typical dilution of maintenance effect on QCH4/milk was detected as a consequence of increasing milk yield and similar significant reduction of QCO2/milk. The results raise challenging questions regarding the rumination patterning of grazing dairy cows and alternatives to reduce ruminant methane emissions in grazing dairy cows.
Copyright © 2015 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.
... Similarly, average herd CH 4 flux was 5.8% of gross energy intake in experiment 2. Lower value in experiment 2 than experiment 1 can be attributed to greater DMI and different diet composition in experiment 2 (corn silage vs. grass silage, corn vs. barley grain). Significant correlations were found between DMI and the flux method CH 4 in experiment 1 and between BW and CH 4 and CO 2 fluxes in experiment 2. Hammond et al. (2013) demonstrated in direct comparisons a good agreement between the flux method and respiration chambers, but emissions were 12% lower with the flux method compared with SF 6 . Waghorn et al. (2013) found spot flux measurements of CH 4 to correlate well with calculated CH 4 emissions on an individual-cow basis. ...
Nutritional and animal-selection strategies to mitigate enteric methane (CH4) depend on accurate, cost-effective methods to determine emissions from a large number of animals. The objective of the present study was to compare 2 spot-sampling methods to determine CH4 emissions from dairy cows, using gas quantification equipment installed in concentrate feeders or automatic milking stalls. In the first method (sniffer method), CH4 and carbon dioxide (CO2) concentrations were measured in close proximity to the muzzle of the animal, and average CH4 concentrations or CH4/CO2 ratio was calculated. In the second method (flux method), measurement of CH4 and CO2 concentration was combined with an active airflow inside the feed troughs for capture of emitted gas and measurements of CH4 and CO2 fluxes. A muzzle sensor was used allowing data to be filtered when the muzzle was not near the sampling inlet. In a laboratory study, a model cow head was built that emitted CO2 at a constant rate. It was found that CO2 concentrations using the sniffer method decreased up to 39% when the distance of the muzzle from the sampling inlet increased to 30 cm, but no muzzle-position effects were observed for the flux method. The methods were compared in 2 on-farm studies conducted using 32 (experiment 1) or 59 (experiment 2) cows in a switch-back design of 5 (experiment 1) or 4 (experiment 2) periods for replicated comparisons between methods. Between-cow coefficient of variation (CV) in CH4 was smaller for the flux than the sniffer method (experiment 1, CV = 11.0 vs. 17.5%, and experiment 2, 17.6 vs. 28.0%). Repeatability of the measurements from both methods were high (0.72-0.88), but the relationship between the sniffer and flux methods was weak (R(2) = 0.09 in both experiments). With the flux method CH4 was found to be correlated to dry matter intake or body weight, but this was not the case with the sniffer method. The CH4/CO2 ratio was more highly correlated between the flux and sniffer methods (R(2) = 0.30), and CV was similar (6.4-8.8%). In experiment 2, cow muzzle position was highly repeatable (0.82) and influenced sniffer and flux method results when not filtered for muzzle position. It was concluded that the flux method provides more reliable estimates of CH4 emissions than the sniffer method. The sniffer method appears to be affected by variable air-mixing conditions created by geometry of feed trough, muzzle movement, and muzzle position.
Copyright © 2015 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.
... Similarly, average herd CH 4 flux was 5.8% of gross energy intake in experiment 2. Lower value in experiment 2 than experiment 1 can be attributed to greater DMI and different diet composition in experiment 2 (corn silage vs. grass silage, corn vs. barley grain). Significant correlations were found between DMI and the flux method CH 4 in experiment 1 and between BW and CH 4 and CO 2 fluxes in experiment 2. Hammond et al. (2013) demonstrated in direct comparisons a good agreement between the flux method and respiration chambers, but emissions were 12% lower with the flux method compared with SF 6 . Waghorn et al. (2013) found spot flux measurements of CH 4 to correlate well with calculated CH 4 emissions on an individual-cow basis. ...
Abstract Text:
There are two new measurement techniques to measure emitted methane (CH4) and carbon dioxide (CO2) from cattle in production systems, the passive concentration measurement method (PCM) and the active gas capture method (AGC). Both systems estimate cattle muzzle CH4 and CO2emissions for short term periods (3-15 min) while cattle visit a feeding station multiple times daily. The objective was to determine if the two techniques yielded comparable results under farm conditions.
A GreenFeed (GF) system was used (C-Lock Inc, Rapid City, SD) that measures individual animal emissions over a feed trough. For AGC, an active airflow (2,000 l/min) was induced around the animal’s muzzle that attracted emissions into a air collection pipe where airflow and CH4 and CO2 concentrations were measured and the average flux was calculated for each visit. For PCM, a concentration sampling intake (at 1 l/min) was placed inside the feed trough, no active airflow was used, and the average CH4 and CO2concentrations for each visit were calculated. 32 Swedish Red dairy cows (BW 664±72 kg, MY 30.2±6.3 kg/d, and DMI 20.1±2.8 kg/d) housed in a free-stall barn had an access to two separate GF units. The diets were fed ad libitum as TMR (60% forages, 40% concentrates on DM basis). The GF were configured for 10 day sampling periods using PCM and AGC repeated twice. The data was analyzed with linear mixed models using the MIXED procedure in SAS. Repeatability (R) was calculated as R = δ2Animal / (δ2Ánimal + δ2Residual).
The cows visited GF on average 2.85 ± 0.95 times per day. For CH4, the between animal coefficient of variation (CV) was greater (11.0 vs. 17.6%) with PMC compared to AGC. Comparing CH4 results for individual animals to determine if ranking was consistent between AGC and PCM, a weak correlation was found between CH4 concentration with PCM and CH4 flux with AGC: CH4 Flux (g/d) = 363 ± 30.5 + 0.058 ± 0.0214 × CH4 (ppm) (R2 = 0.13; RMSE = 52.1). For CH4/CO2 ratio, CV values were similar (6.4 and 6.6%) but averaged CH4/CO2 ratio was greater (P = 0.001) with PMC (0.107) compared with AGC (0.094). The repeatability for AGC and PCM were high (0.72- 0.74).
It is concluded that PCM methods are not sufficient for ranking animal’s emissions on farms. Measuring concentration passively is not the same as measuring fluxes.
Keywords: Methane, cattle, emissions
... The technology has been evaluated in dairy cows (Madsen et al., 2010;Lassen et al., 2012) and has potential for measuring animals at pasture (Garnett, 2012;Storm et al., 2012). Such systems are capable of estimating CH 4 emissions from livestock, but deployment and replication must be carefully considered to ensure adequate numbers of measurements are obtained (Hammond et al., 2013). ...
A total of 2600 methane ( CH: 4) and 1847 CO2 measurements of sheep housed for 1 h in portable accumulation chambers ( PAC: ) were recorded at 5 sites from the Australian Sheep CRC Information Nucleus, which was set up to test leading young industry sires for an extensive range of current and novel production traits. The final validated dataset had 2455 methane records from 2279 animals, progeny of 187 sires and 1653 dams with 7690 animals in the pedigree file. The protocol involved rounding up animals from pasture into a holding paddock prior to the first measurement on each day, then measuring in groups of up to 16 sheep over the course of the day. CH4 emissions declined linearly (with different slopes for each site) with time since the sheep were drafted into the holding area. After log transformation, estimated repeatability ( RPT: ) and heritability ( H: (2)) of liveweight-adjusted CH4 emissions averaged 25% and 11.7% respectively for a single 1-h measurement. Sire x site interactions were small and non-significant. Correlations between estimated breeding values ( EBV: ) for methane emissions and published EBV for production traits were used as approximations to genetic correlations. Apart from small positive correlations with weaning and yearling weights (r = 0.21-0.25, P < 0.05), there were no significant relationships between production trait and methane EBV (calculated from a model adjusting for liveweight by fitting separate slopes for each site). To improve accuracy, future protocols should use the mean of two (rpt = 39%, h(2) = 18.6%), or three (rpt = 48%, h(2) = 23.2%) PAC measurements. Repeat tests under different pasture conditions and time of year should also be considered, as well as protocols measuring animals directly off pasture instead of rounding them up in the morning. Reducing the time in the PAC from 1 h to 40 min would have a relatively small effect on overall accuracy and partly offset the additional time needed for more tests per animal. Field testing in PACs has the potential to provide accurate comparisons of animal and site methane emissions, with potentially lower cost/increased accuracy compared to alternatives such as SF6 tracers or open path lasers. If similar results are obtained from tests with different protocols/seasonal conditions, use of PAC measurements in a multi-trait selection index with production traits could potentially reduce methane emissions from Australian sheep for the same production level.
... Recent comparisons by Hammond et al. (2013) show a high correlation between DMP measured in RC and estimated by a GreenFeed unit. Waghorn et al. (2013) also found GreenFeed estimates of DMP for dairy cattle closely matched DMP estimated from animal productivity and live weight change. ...
A short term enteric methane emission measurement is not identical to a measure of daily methane production (DMP) made in a respiration chamber (RC). While RC curtail most variation except that from quantity and composition of feed supplied, all short-term measurements contain additional sources of variation. The points of difference can include measurement time(s) relative to feeding, feed intake before measurement, animal behaviour in selection of diet and level of activity before measurement. For systems where a short-term emission measurement is made at the same time in the daily feeding cycle (e.g. during twice-daily milking) scaling up of short-term emission rates to estimate DMP is feasible but the scaling coefficient(s) will be diet dependent. For systems such as GreenFeed where direct emission rates are measured on occasion throughout day and night, no scaling up may be required to estimate DMP. For systems where small numbers of emission measures are made, and there is no knowledge of prior feed intake, such as for portable accumulation chambers, scaling to DMP is not currently possible. Even without scaling up to DMP, short-term measured emission rates are adequate for identifying relative emission changes induced by mitigation strategies and could provide the data to support genetic selection of ruminants for reduced enteric emissions.
... The SF 6 tracer method has been shown to produce larger variability than respiration chambers (Grainger et al., 2007;Hammond et al., 2009;Clark, 2010;Moate et al., 2011), but it enables emissions to be determined in a large number of animals and in free grazing conditions. Novel in vivo approaches, such as the use of CO 2 as a tracer gas (Madsen et al., 2010) and the Green-Feed system (C-Lock, Inc., Rapid City, SD; Huhtanen et al., 2013;Hammond et al., 2013b), have also been proposed. Therefore, when evaluating mitigation practices, it is important to examine critically the measurement methods used, particularly in relation to CH 4 production. ...
The goal of this review was to analyze published data related to mitigation of enteric methane (CH4) emissions from ruminant animals to document the most effective and sustainable strategies. Increasing forage digestibility and digestible forage intake was one of the major recommended CH4 mitigation practices. Although responses vary, CH4 emissions can be reduced when corn silage replaces grass silage in the diet. Feeding legume silages could also lower CH4 emissions compared to grass silage due to their lower fiber concentration. Dietary lipids can be effective in reducing CH4 emissions, but their applicability will depend on effects on feed intake, fiber digestibility, production, and milk composition. Inclusion of concentrate feeds in the diet of ruminants will likely decrease CH4 emission intensity (Ei; CH4 per unit animal product), particularly when inclusion is above 40% of dietary dry matter and rumen function is not impaired. Supplementation of diets containing medium to poor quality forages with small amounts of concentrate feed will typically decrease CH4 Ei. Nitrates show promise as CH4 mitigation agents, but more studies are needed to fully understand their impact on whole-farm GHG emissions, animal productivity, and animal health. Through their effect on feed efficiency and rumen stoichiometry, ionophores are likely to have a moderate CH4 mitigating effect in ruminants fed high-grain or mixed grain-forage diets. Tannins may also reduce CH4 emissions, although in some situations intake and milk production may be compromised. Some direct-fed microbials, such as yeast-based products, might have a moderate CH4-mitigating effect through increasing animal productivity and feed efficiency, but the effect is likely to be inconsistent. Vaccines against rumen archaea may offer mitigation opportunities in the future, although the extent of CH4 reduction is likely to be small, and adaptation by ruminal microbes and persistence of the effect is unknown. Overall, improving forage quality and the overall efficiency of dietary nutrient use is an effective way of decreasing CH4 Ei. Several feed supplements have a potential to reduce CH4 emission from ruminants, although their long-term effect has not been well-established and some are toxic or may not be economically feasible.
Globally, livestock is an important contributor to methane (CH4) emissions. This paper reviewed the various CH4 measurement and estimation techniques and mitigation approaches for the livestock sector. Two approaches for enteric livestock CH4 emission estimation are the top-down and bottom-up. The combination of both could further improve our understanding of enteric CH4 emission and possible mitigation measures. We discuss three mitigation approaches: reducing emissions, avoiding emissions, and enhancing the removal of emissions from livestock. Dietary management, livestock management, and breeding management are viable reducing emissions pathways. Dietary manipulation is easily applicable and can bring an immediate response. Economic incentive policies can help the livestock farmers to opt for diet, breeding, and livestock management mitigation approaches. Carbon pricing creates a better option to achieve reduction targets in a given period. A combination of carbon pricing, feeding management, breeding management, and livestock management is more feasible and sustainable CH4 emissions mitigation strategy rather than a single approach
Methane (CH4) is a natural by-product of microbial fermentation of carbohydrates and amino acids in the rumen and the hindgut of farm animals. Methane is a powerful greenhouse gas, therefore, there has been increasing interest in reducing methane emissions from livestock. Calorimetry chambers have been built, in part, to measure emissions and assess effects of mitigating effects of dietary manipulations. The objective of this chapter is to review various types of indirect calorimetry chambers developed to measure CH4 emissions from livestock. Indirect calorimetry chambers allow measurement of gaseous exchange to high degree of accuracy. However, confinement in small spaces results in altered animal behaviour, including reduced feed intake. Modifications that use polycarbonate has improved animal welfare concerns while maintaining high accuracy of measured gases. Principles of indirect calorimetry were used to build ventilated hoods (head box) to measure gas exchange. Units that are suitable for group of animals have also been constructed to measure methane emissions based on the same principles. All of the above techniques cannot be used for animals on pasture, therefore, tracer based techniques such as the sulphur hexafluoride or GreenFeed systems have been developed. Compared to indirect calorimetry methods, tracer methods do not measure whole animal emissions and there is high animal-to-animal variability associated with measurements. So, frequent sampling and more animals are required to improve accuracy of measurements. Indirect calorimetry methods are considered to be the gold standard in measuring methane emissions. However, for pasture based systems, tracer methods are more suited and will continue to be used.
Significance
Methane from enteric fermentation in the ruminant digestive system is a major contributor to anthropogenic greenhouse gas emissions in the United States and worldwide. Methane is also a net loss of feed energy to the animal. This study was undertaken to investigate the effect of a methane inhibitor on enteric methane emissions from lactating dairy cows. The experiment demonstrated that, under industry-relevant conditions, the inhibitor persistently decreased by 30% enteric methane emissions, without negatively affecting animal productivity. The spared methane energy was partially used for tissue synthesis, which led to a greater body weight gain by the inhibitor-treated cows. If adopted, this mitigation practice could lead to a substantial reduction of greenhouse gas emissions from the ruminant livestock sector.
Abstract Text:
Real time measurements of CH4 (QCH4) and CO2 (QCO2) fluxes were used in a pilot study to estimate heat production1 (HP) and energy conversion efficiency in lactating dairy cows. Oxygen utilization (QO2) was estimated according to the respiration quotient2. Eleven multiparous and 4 primiparous lactating Holstein cows averaging 176 ± 34 DIM, 42.9 ± 6.8 kg of milk yield and 681 ± 48 kg of BW were blocked by DIM, parity, and DMI (as % of BW) and, within each block, randomly assigned to 1 of 2 treatments: restricted intake (RI) (90% DMI) or ad libitum intake (AI) according to a crossover design. Each experimental period lasted 22 d with 14 d for treatments adaptation and 8 d for data and sample collection. Diets contained (DM basis): 40% corn silage, 12% grass-legume haylage, and 48% concentrate. Spot gas measurements were taken in 5-min sampling periods from all cows using a portable automated head chamber system [GreenFeed® (GF); C-Lock Inc., Rapid City, SD] with intervals of 12 h between the 2 daily samplings. Sampling points were advanced 2 h from a day to the next to yield 14 gas samplings/cow over 7 d to account for diurnal variation in QCH4 and QCO2. Data were analyzed using the Fit Model procedure in JMP, and least square means are reported. Cows on RI converted more feed gross energy3 into milk energy4 (28.3 vs. 27.0%, SEM = 0.63; P = 0.04) and more DMI into metabolizable energy5 than AI cows (11.8 vs. 11.3 MJ/kg of DMI; SEM = 0.22 P = 0.02). Conversely, RI cows yielded more HP/kg of DMI (6.65 vs. 6.36 MJ/kg; SEM = 0.18; P = 0.04). Our results suggest that the proposed methodology has potential to identify more efficient dairy cows according to real time measurements of QCH4 and QCO2 using the GF.
Equations used for estimations:
1Estimated HP MJ/cow/d = [(3.86 × QO2) + (1.2 × QCO2) – (0.518 × QCH4)] × 4.184/1000 (Brouwer, 1965)
2QO2/QCO2 = 0.95 (Madsen et al., 2010)
3Gross energy intake MJ/cow/d = [dietary CP% × DMIkg × 17 × 0.6] × 4.184 (IPCC, 2006)
4Milk energy MJ/cow/d = [(0.384 × fat%) + (0.223 × protein%) + (0.199 × lactose%) – 0.108] × milk yield kg/cow/d (AFRC, 1993)
5Metabolizable energy MJ/cow/d = HP + Milk energy ± (19.99 × kg of mobilized weight) (AFRC, 1990)
Keywords: energy conversion efficiency, heat production, GreenFeed
Previous experiments have suggested that estimates of methane (CH 4) emissions from ruminant animals made using the sulphur hexafluoride (SF6) tracer might be influenced by the permeation rate of SF6 (PR). This study examined the latter issue with cattle. For this, analyses of data sets from two grazing trials involving large herds (exps. 1 and 2) and a specifically designed controlled trial (exp. 3) were conducted. Individual daily CH4 emissions from 296 (exp. 1) and 388 (exp. 2) Friesian x Jersey cows in mid-lactation were measured with herds subdivided into four (exp. 1) or five (exp. 2) measurement groups and dry matter intake (DMI) estimated by energy metabolism algorithms. The ranges of tracer PR in exps. 1 and 2 were 2.624-5.689 and 2.214-3.594 mg d-1, respectively. Experiment 3 was conducted using 12 rumenfistulated beef steers pen-fed on lucerne silage and design arranged as a 4 x 4 Latin square with three replications. Permeation tubes with four levels of nominal PR (three tubes each): low (L), medium (M), medium-high (MH) and high (H) were randomly assigned to four rumen deployment sequences (L-M-MH-H, H-MH-M-L, MH-L-H-M and M-H-L-MH). The grazing experiments revealed a positive effect of PR on the CH4 emission estimates (1 mg SF6 d-1 counting for 0.6-2.3 g kg -1 DMI), but this effect was significant (R2 =0.06-0.23, P <0.05) only when there was a large range in PR (exp. 1), whereas with a narrower PR range (exp. 2) the effect was not significant (R2 <0.04, P>0.05). Experiment 3 revealed that the influence of PR upon CH4 emission estimates was linear. It is concluded that despite an influence of PR on CH4 emission estimates, accuracy and precision of the tracer technique is warranted provided that PR are used in a narrow range and balanced between the experimental treatments.
The sulphur hexafluoride (SF6) tracer technique enables determination of enteric methane emissions from large numbers of individual ruminant animals. The objective of this research was to identify and correct substantial errors within the SF6 technique. Six experiments were undertaken using respiration chamber, laboratory or SF6 techniques. Experiment 1 used respiration chambers to demonstrate that the daily pattern of methane emissions from dairy cows was related to their pattern of feed intake. In contrast, the daily emission of SF6 from these cows was constant and independent of the pattern of methane emission. This finding supports the contention that in order to accurately determine daily methane emissions using the SF6 technique, it is necessary that gases are collected continuously at a constant rate for 24 h. Since development of the SF6 technique in 1993, it has been propounded that capillary-tube flow restrictors achieved a constant rate of sample collection into evacuated gas collection canisters. Laboratory experiments 2, 3, 4 and 5 demonstrated that, when capillary-tube flow restrictors are used, the rate of sample collection declined and caused a bias of up to 15.6% in calculated methane emissions. This error was caused by an interaction between the declining sample collection rate and the pattern of an animal's methane emission over 24 h. In contrast, orifice plate flow restrictors maintained a constant sample collection rate at canister pressures <0.31 atm and thereby minimised the decline in sample collection rate. Experiment 5 also demonstrated that sample collection using orifice plate flow restrictors, combined with initial (<0.03 atm) and final (<0.49 atm) canister pressures, substantially reduced measurement error. Accuracy of the modified SF6 technique, incorporating orifice plate flow restrictors for 24 h sample collection, was validated in Experiment 6. The mean (S.D.) methane yield (g CH4/kg DMI) of eight cows did not differ (P = 0.135) when determined using the modified SF6 technique 22.3 (1.44) or chambers 21.9 (1.65). In addition, the between-animal coefficient of variation for methane yield determined using the modified SF6 technique (6.5%) was similar to that determined using chambers (7.5%). Consequently the modified SF6 technique enables the statistical power of experiments to be increased or their size decreased. We conclude that the modified SF6 technique reduced error associated with SF6 release, sample collection and analysis. It is recommended that the modified SF6 technique should be used in preference to the original SF6 technique for determination of enteric methane emissions from ruminants.
A short term enteric methane emission measurement is not identical to a measure of daily methane production (DMP) made in a respiration chamber (RC). While RC curtail most variation except that from quantity and composition of feed supplied, all short-term measurements contain additional sources of variation. The points of difference can include measurement time(s) relative to feeding, feed intake before measurement, animal behaviour in selection of diet and level of activity before measurement. For systems where a short-term emission measurement is made at the same time in the daily feeding cycle (e.g. during twice-daily milking) scaling up of short-term emission rates to estimate DMP is feasible but the scaling coefficient(s) will be diet dependent. For systems such as GreenFeed where direct emission rates are measured on occasion throughout day and night, no scaling up may be required to estimate DMP. For systems where small numbers of emission measures are made, and there is no knowledge of prior feed intake, such as for portable accumulation chambers, scaling to DMP is not currently possible. Even without scaling up to DMP, short-term measured emission rates are adequate for identifying relative emission changes induced by mitigation strategies and could provide the data to support genetic selection of ruminants for reduced enteric emissions.
Measurements of enteric methane (CH4) emissions from individual animals have traditionally been made with indirect calorimetry techniques, which are both accurate and reliable. However, the expense and need for animal training and the extent to which calorimetric results can be extrapolated to free-ranging animals have been questioned and stimulated the development of the sulfur hexafluoride (SF6) tracer technique. The tracer technique is now widely used in New Zealand and many other countries for CH4 emission measurements on grazing and pen-fed cattle, sheep, deer and alpacas. Few studies with cattle and sheep have examined the validity of the SF6 tracer technique. Most of these studies have concluded that estimations of CH4 emission by this technique do not differ from those of calorimetric techniques, though some exceptions have been reported. There is general agreement that the tracer technique is associated with large between-animal variability in the CH4 emission estimates from animals on the same diet, but it remains unknown whether this is due to the environment, housing conditions or the technique itself. High within-animal variability has also been reported from tracer CH4 measurements. There is growing evidence that CH4 emission estimates by the tracer technique are positively influenced by the permeation rate (PR) of the SF6 gas from permeation tubes and it has been suggested that fate of the tracer in the rumen rather than unrepresentative breath sample collection is the likely reason for the latter. It is concluded that although some issues related to the tracer technique need to be clarified, using a narrow range in PR and balancing of PR between treatments should be practised in order to overcome the relationship between PR and CH4 emission estimates.
Methane, in addition to being a significant source of energy loss to the animal that can range from 0·02 to 0·12 of gross energy intake, is one of the major greenhouse gases being targeted for reduction by the Kyoto protocol. Thus, one of the focuses of recent research in animal science has been to develop or improve existing methane prediction models in order to increase overall understanding of the system and to evaluate mitigation strategies for methane reduction. Several dynamic mechanistic models of rumen function have been developed which contain hydrogen gas balance sub-models from which methane production can be predicted. These models predict methane production with varying levels of success and in many cases could benefit from further development. Central to methane prediction is accurate volatile fatty acid prediction, representation of the competition for substrate usage within the rumen, as well as descriptions of protozoal dynamics and pH. Most methane models could also largely benefit from an expanded description of lipid metabolism and hindgut fermentation. The purpose of the current review is to identify key aspects of rumen microbiology that could be incorporated into, or have improved representation within, a model of ruminant digestion and environmental emissions.
H. 2007. The possible influence of intra-ruminal sulphur hexafluoride release rates on calculated methane emissions from cattle. Can. J. Anim. Sci. 87: 269–275. Estimates of methane (CH 4) production from grazing animals are routinely made using the sulphur hexafluoride (SF 6) tracer technique. While this technique is generally regarded as useful, some investigators report a higher variability in measurements when compared with calorimetry. The SF 6 technique is a marker dilution method in which a known release rate of SF 6 from an intra-ruminal perme-ation tube is used to calculate CH 4 emissions from the ratio of SF 6 :CH 4 in expired breath. The release rate of SF 6 is unique for each tube, and although calculated CH 4 emissions should be independent of SF 6 release rate, an analysis of research conducted in New Zealand has suggested a possible influence of SF 6 release rate upon calculated CH 4 emissions. A modified cross-over design, with two groups of six steers given either one (2.878 mg SF 6 d –1) or two (7.336 mg SF 6 d –1) permeation tubes and offered either energy maintenance (M) or 2 × M levels of feed intake was undertaken to determine the effect of SF 6 release rate and intake on calculated CH 4 emissions. A high SF 6 release rate elevated the calculated CH 4 emission per day (P < 0.001) and per kg dry mat-ter intake (kg DMI) by 19% (P < 0.001) irrespective of the level of intake. Release rate of SF 6 can affect the calculated CH 4 emis-sions from animals when employing the SF 6 tracer technique.
The objective of this study was to investigate whether measurement of methane emissions by individual dairy cows during milking could provide a useful technique for monitoring on-farm methane emissions. To quantify methane emissions from individual cows on farm, we developed a novel technique based on sampling air released by eructation during milking. Eructation frequency and methane released per eructation were used to estimate methane emission rate. For 82 cows, methane emission rate during milking increased with daily milk yield (r = 0.71), but varied between individuals with the same milk yield and fed the same diet. For 12 cows, methane emission rate recorded during milking on farm showed a linear relationship (R² = 0.79) with daily methane output by the same cows when housed subsequently in respiration chambers. For 42 cows, the methane emission rate during milking was greater on a feeding regimen designed to produce high methane emissions, and the increase compared with a control regimen was similar to that observed for cows in respiration chambers. It was concluded that, with further validation, on-farm monitoring of methane emission rate during milking could provide a low-cost reliable method to estimate daily methane output by individual dairy cows, which could be used to study variation in methane, to identify cows with low emissions, and to test outcomes of mitigation strategies.
1. Twenty Friesian steers (225 kg live weight) were fed on mid- (M) (June-July) and late- (L) (August- September) season crops of either fresh perennial ryegrass (Loliumperenne cv. Melle) (G) or white clover (Trifolium repens cv. Blanca) (C). Each of the forage diets was offered at three restricted planes of nutrition above main- tenance to compare the effect of forage species on the efficiency of energy utilization. All diets were harvested daily from swards of regrowth forage of intended equivalent digestibility.
2. Faecal and urine excretions were measured for 7 and 5 d respectively, followed by two consecutive 24 h measurements of methane, carbon dioxide and oxygen exchange in open-circuit respiration chambers.
3. The apparent digestibility of the energy in perennial ryegrass (0.759) was marginally higher (P < 0.01) than that in white clover (0.748);the mid- and late-season forages were of similar (P > 0.05)digestibilities. Metabolizable energy (ME):digestible energy (DE) in diet G (0.837) was significantly (P < 0,001) different from that in diet C (0.812). The partition of energy losses when expressed as MJ/GJ gross energy intake (GEI) indicated that energy lost as methane was not significantly different (P > 0.05) either between forages (G 62.8, C 63.4) or between seasons (M 63.2, L 63.1). Energy excretion in urine was higher for cattle fed on diet C (77.5) compared with diet G (60.5)(P < 0.001). Heat production was similar (P 0.05) between forages (G 480, C 478), but lower (P < 0.01) for L (471) compared with M(486). Energy retention (by difference) was lower (P < 0.001) for diet C (132) than G (156) and for M (138) than L (149) (P < 0.05).
4. Parallel-line analysis of unscaled ME intake (MEI) in relation to retained energy (RE; MJ/d) indicated that the efficiency of utilization (k r ) was similar (P > 0.05) between perennial ryegrass (0.42) and white clover (0.46). Linear extrapolation of the values to zero energy retention indicated that maintenance requirements of ME (E m MJ/d) were 23.3 for diet G and 28.8 for diet C. The extrapolated Emwhen expressed in relation to a measured fasting heat production (FHP) of 22.8 (MJ/d) resulted in a derived efficiency of utilization of ME for maintenance (k m ) of 0.97 (G) and 0.79 (C), suggesting an underestimate of E m for diet G.
5. Asymptotic exponential curves (representing the law ofdiminishing returns) were fitted to the unscaled values, ME1 and RE (MJ/d), and extrapolated to zero energy retention and zero energy intake. The derived estimates of FHP (MJ/d) 18.0 (G) and 22.0 (C) were not significantly different (P > 0.05) from the observed value of 22.8 MJ/d. Using the measured FHP as additional data points, the exponential model accounted for significantly more variance (P < 0,001) compared with the linear regression method of analysis. Exponential analysis resulted in estimates of Em (MJ/d) of 29.04 for diet G and 31.80 for C. The k, for each forage was calculated, assuming linearity of response, as 0.78 (G) and 0.72 (C). The calculation of k, at fixed positions on the exponential curve related to ME1 (expressed as multiples of Em)indicated that above 1.65 E m , k t was significantly higher for C than G (P < 0.05). With increasing plane of nutrition kf declined from 0.53 to 0.29 (G) and 0.55 to 0.36 (C) over the ME1 range measured during the experiment.
Methane production has been measured from lambs fed contrasting forages. This work has been driven by the need to reduce greenhouse gas emissions from agriculture and to determine energy losses to methane from contrasting diets. Young ram lambs were fed either fresh ryegrass/white clover pasture, lucerne (also pelleted lucerne), sulla, chicory, red clover, Lotus pedunculatus (lotus) and mixtures of sulla and lucerne, sulla and chicory and chicory with red clover. The effects of condensed tannin (CT) in lotus on methane production were also measured. The trials were carried out indoors with sheep held in metabolism crates to enable an accurate measurement of intake and digestibility as well as methane production. Principal findings were a two-fold range in emissions from 11.5g CH4/kg dry matter intake (DMI) with lotus to 25.7g CH4/kg DMI with pasture and a 16% reduction in methane production due to the CT in lotus. This range in emissions from good quality forages represents a loss of about 7-11% of metabolisable energy and presents a clear direction for future research to better utilise the feeding value of pastures and reduce greenhouse gas (GHG) emissions from agriculture. High quality perennial forages should be used where practical, and researchers need to identify plant parameters responsible for the variation in methane emissions. Research must focus on rapid passage of digesta through the rumen of grazing animals and will involve manipulation of the fibre content of grasses. Introduction of CT into diets is a likely target to reduce methane production. Improving the rapidly digestible constituents of forages is another opportunity, but difficult to target. Keywords: condensed tannins, forage quality, forages, greenhouse gases, methane emissions, sheep
Intensive farming focusing on monoculture grass species to maximise forage production has led to a reduction in the extent and diversity of species-rich grasslands. However, plant communities with higher species number (richness) are a potential strategy for more sustainable production and mitigation of greenhouse gas (GHG) emissions. Research has indicated the need to understand opportunities that forage mixtures can offer sustainable ruminant production systems. The objective of the two experiments reported here were to evaluate multiple species forage mixtures in comparison to ryegrass-dominant pasture, when conserved or grazed, on digestion, energy utilisation, N excretion, and methane emissions by growing 10–15 month old heifers. Experiment 1 was a 4 × 4 Latin square design with five week periods. Four forage treatments of: (1) ryegrass (control); permanent pasture with perennial ryegrass (Lolium perenne); (2) clover; a ryegrass:red clover (Trifolium pratense) mixture; (3) trefoil; a ryegrass:birdsfoot trefoil (Lotus corniculatus) mixture; and (4) flowers; a ryegrass:wild flower mixture of predominately sorrel (Rumex acetosa), ox-eye daisy (Leucanthemum vulgare), yarrow (Achillea millefolium), knapweed (Centaurea nigra) and ribwort plantain (Plantago lanceolata), were fed as haylages to four dairy heifers. Measurements included digestibility, N excretion, and energy utilisation (including methane emissions measured in respiration chambers). Experiment 2 used 12 different dairy heifers grazing three of the same forage treatments used to make haylage in experiment 1 (ryegrass, clover and flowers) and methane emissions were estimated using the sulphur hexafluoride (SF6) tracer technique. Distribution of ryegrass to other species (dry matter (DM) basis) was approximately 70:30 (clover), 80:20 (trefoil), and 40:60 (flowers) for experiment 1. During the first and second grazing rotations (respectively) in experiment 2, perennial ryegrass accounted for 95 and 98% of DM in ryegrass, and 84 and 52% of DM in clover, with red clover accounting for almost all of the remainder. In the flowers mixture, perennial ryegrass was 52% of the DM in the first grazing rotation and only 30% in the second, with a variety of other flower species occupying the remainder. Across both experiments, compared to the forage mixtures (clover, trefoil and flowers), ryegrass had a higher crude protein (CP) content (P < 0.001, 187 vs. 115 g kg −1 DM) and DM intake (P < 0.05, 9.0 vs. 8.1 kg day −1). Heifers in experiment 1 fed ryegrass, compared to the forage mixtures, had greater total tract digestibility (g kg −1) of DM (DMD; P < 0.008, 713 vs. 641) and CP (CPD, P < 0.001, 699 vs. 475), and used more intake energy (%) for body tissue deposition (P < 0.05, 2.6 vs. −4.9). For both experiments, heifers fed flowers differed the most compared to the ryegrass control for a number of measurements. Compared to ryegrass, flowers had 40% lower CP content (P < 0.001, 113 vs. 187 g kg −1), 18% lower DMD (P < 0.01, 585 vs. 713 g kg −1), 42% lower CPD (P < 0.001, 407 vs. 699 g kg −1), and 10% lower methane yield (P < 0.05, 22.6 vs. 25.1 g kg −1 DM intake). This study has shown inclusion of flowers in forage mixtures resulted in a lower CP concentration, digestibility and intake. These differences were due in part to sward management and maturity at harvest. Further research is needed to determine how best to exploit the potential environmental benefits of forage mixtures in sustainable ruminant production systems.
Predictable release of sulphur hexafluoride (SF6) tracer gas from permeation tubes into the reticulo-rumen is necessary to estimate methane emissions from ruminants using the SF6 tracer technique. Any discrepancy between the laboratory determined rate of SF6 release from permeation tubes and the actual rate of release in the reticulo-rumen would bias calculated methane emissions. The purpose of this investigation was to determine the effect of temperature, submersion and orientation on the rate of SF6 release from permeation tubes. Four experiments were undertaken. Experiment 1 determined that release of SF6 increased by 2.5 ± 0.14% per degree Celsius increase in temperature between 37 and 41 °C (P < 0.001). Experiment 2 determined that the Arrhenius equation can be used to describe the temperature dependence of SF6 release rate from permeation tubes between 0 and 70 °C, consistent with a change in release rate of 2.3 ± 0.08% per degree Celsius change in temperature. Experiment 3 determined that submersion of permeation tubes in water did not affect the rate of SF6 release (P = 0.13). Experiment 4 determined that SF6 release rate was not influenced by permeation tube orientation (P = 0.42). In addition we determined the activation energy of permeation, Ep, describing the overall temperature dependence of SF6 permeation flux from permeation tubes, to be 18,424 ± 680 joules/mole. This research implies that the short-term release rate of SF6 from permeation tubes within the reticulo-rumen will vary in response to temperature change due to animal, diet and/or environmental factors. A short term decrease in temperature of reticulo-rumen contents, induced by drinking cold water, is expected to have a larger influence on the accuracy of estimated methane emission derived from time-averaged sampling periods less than 24 h. Use of the SF6 technique to detect differences in enteric methane emissions due to diet or between animal species may be confounded by diet or genetic effects on body temperature. Unless the effect of temperature is managed through careful implementation of the technique, substantial errors could be caused as illustrated by the following example: a +2 °C error in calibration temperature (41 °C), and a -2 °C discrepancy between the actual (37 °C) and assumed reticulo-rumen temperature (39 °C), could bias estimated methane emissions by approximately +10%.
Forage chicory (Cichorium intybus) has the potential to mitigate methane emissions from ruminants. It was reported that the reduction can be up to 30% compared with perennial ryegrass (Lolium perenne). To accurately evaluate the reduction, fresh chicory and perennial ryegrass in the vegetative state were fed to 24 wethers, 8 of which rumen-fistulated, at 1.3 and 2.2 times maintenance metabolisable energy requirements. Dry matter (DM) intake, whole tract apparent digestibility, rumen fermentation parameters and rumen liquid passage rate were measured in metabolism crates, and methane emissions determined using a calorimetric technique. Chemical analyses showed that chicory contained less DM, organic matter (OM), crude protein, neutral detergent fibre (aNDF), acid detergent fibre (ADF), cellulose and hemicellulose, but more hot water-soluble carbohydrate and pectin, than perennial ryegrass. Methane yield (g/kg DM intake) of wethers fed chicory did not differ from that of those fed perennial ryegrass. Yield was lower at the high versus the low feeding level of ryegrass. Apparent digestibility of DM and OM was higher, and aNDF, ADF, hemicellulose and cellulose was lower, in wethers fed chicory versus perennial ryegrass. In situ DM degradation rate of chicory was higher than that of perennial ryegrass. Rumen liquid passage rate was the same for wethers fed the two forages and higher at the high feeding level. The reduction in methane emissions by feeding vegetative chicory to wethers was limited, but increased feeding level reduces methane yields per unit of DM intake.
Predictable release of sulphur hexafluoride (SF6) from permeation tubes is critical for determination of enteric methane emissions from ruminants using the calibrated tracer technique. Experiments comparing respiration chambers and the SF6 technique indicate
that prolonged deployment of SF6 tubes causes overestimation of methane emissions. We report three studies investigating release rate of SF6 from permeation tubes. Experiment 1 investigated if SF6 was released by routes other than the polytetrafluoroethylene (PTFE) membrane. Replacement of the membrane with an impervious disk prevented SF6 release, confirming that SF6 release occurs only through the PTFE membrane. Experiment 2 investigated the effect of frit exposure to the rumen environment and reticulo-rumen residence duration upon SF6 release rate. Three treatments were applied: (i) tubes with exposed frits (Control), (ii) tubes with exposed frits previously incubated for 152 d in the reticulo-rumen (Exposed-frit) and (iii) tubes incorporating an external membrane to prevent frit contamination during 152 d incubation in the reticulo-rumen (Protected-frit). These tubes were then used to determine methane yield. Tubes of each treatment were also retained in an incubator to determine SF6 release rate concurrent to the in vivo experiment. Decline of SF6 release was not related to frit exposure to the reticulo-rumen environment. Methane yield determined using Exposed-frit and Protected-frit tubes was 21% greater than that estimated with Control tubes (P<0.01). Concurrent SF6 release, from Exposed-frit and Protected-frit tubes retained within an incubator was similarly reduced by 22% relative to Control tubes, indicating that decline of SF6 release rate is a function of time elapsed post-calibration, unrelated to tube reticulo-rumen residence duration per se. Experiment 3 was conducted to determine the cause of the in vivo decline in SF6 release. Three pre-treatments were applied to PTFE membranes; untreated (Control-PTFE), 165 d rumen exposure (Rumen-PTFE) and 165 d SF6 exposure (SF6-PTFE). Pre-treated membranes were used to construct new permeation tubes. Release rate from SF6-PTFE tubes was 36% less than from control tubes and 35% less than from Rumen-PTFE tubes (P<0.001). Release rate from Rumen-PTFE tubes did not differ from control tubes (P>0.05). Post-calibration decline in SF6 release rate from permeation tubes results from exposure of PTFE membranes to SF6 rather than reticulo-rumen exposure. We conclude that ‘dry’ incubation of permeation tubes in a laboratory to determine the rate of SF6 release is valid. However, post-calibration decline in SF6 release must be accounted for to prevent over-estimation of methane emissions.
Enteric CH4 contributes about one third of New Zealand's greenhouse gas emissions. Measurements from our laboratory using the sulfur hexafluoride (SF6) technique suggested much lower CH4 yields (as gCH4/kg dry matter (DM) intake) from sheep fed fresh white clover (Trifolium repens) compared with fresh perennial ryegrass (Lolium perenne). Thus, white clover offers an opportunity to reduce CH4 emissions from pastoral based ruminant livestock systems if its lower CH4 yield can be confirmed using respiration chambers. This study was comprised of 2 experiments where good nutritional quality freshly harvested white clover and perennial ryegrass were fed to 16 sheep in Experiment 1 (8/diet) and 32 sheep in Experiment 2 (16/diet). Intakes were about 1.6 times metabolizable energy requirements for maintenance (×MEm) in Experiment 1 and 0.8×MEm and 2.0×MEm in Experiment 2 (8/diet/feeding level). In both experiments sheep had a 10 d acclimatization to their diets and CH4 emissions were measured in respiration chambers for 2 consecutive days. Methane yield (gCH4/kg DM intake) was 12% lower (P=0.04) for white clover (19.8) compared with ryegrass fed sheep (22.5) in Experiment 1. In Experiment 2, there were no effects of forage on CH4 yield (as gCH4/kg DM intake) at 0.8×MEm (27.1 and 25.5, respectively) but, at 2.0×MEm, CH4 yield (as gCH4/kg DM intake) was 7% higher (P=0.05) for white clover (23.4) compared with ryegrass (21.7). Analyses of combined data from both experiments show that there were no overall dietary effects on CH4 yield, but increased intakes reduced CH4 yield (P
Published reports of CH4 yields as g CH4/kg dry matter (DM) intake suggest that emissions from sheep fed fresh forage chicory (Cichorium intybus) are about 30% lower than from those fed fresh ryegrass. In this study, 2 year old wethers (16; 54±3.8kg liveweight) were fed either mature chicory or perennial ryegrass at 1.3 times maintenance metabolisable energy requirements in the late spring/early summer of 2009. Methane emissions were determined using individual animal respiration chambers. Feeds differed in their chemical composition with chicory containing 856g/kg organic matter (OM), 117g/kg crude protein (CP) and 281g/kg neutral detergent fibre (aNDF), whereas ryegrass contained 916g/kg OM, 85g/kg CP and 499g/kg aNDF. The DM intake was similar for both forages at 0.76kg/d, and CH4 yields did not differ between forages being 22.8 and 23.8g CH4/kg DM intake for chicory and ryegrass, respectively. In vitro incubations of chicory and perennial ryegrass in the vegetative or mature states had similar CH4 yields. Despite large differences in chemical composition, especially aNDF, chicory and ryegrass had similar CH4 yields in vitro and in vivo. Chicory is not a viable alternative to perennial ryegrass for mitigating CH4 in pastoral based sheep production systems.This paper is part of the special issue entitled: Greenhouse Gases in Animal Agriculture – Finding a Balance between Food and Emissions, Guest Edited by T.A. McAllister, Section Guest Editors: K.A. Beauchemin, X. Hao, S. McGinn and Editor for Animal Feed Science and Technology, P.H. Robinson.
Attempts to evaluate the sulphur hexafluoride (SF6) tracer technique to estimate CH4 emissions from ruminants have yielded mixed results. These studies either used SF6 permeation tubes with a long history of use in animals, involved small number of animals or used partial animal enclosure. Our study was conducted with a relatively large number of experimental sheep and controlled variables regarding the permeation rate (PR) of SF6. Twenty four sheep housed in a covered yard and fed lucerne silage to achieve common feed intakes among individuals in the study were administered fresh SF6 permeation tubes. Following 10d acclimatisation in pens, sheep were staggered in 3 groups of 8 each in order to match availability of 8 respiration chambers. Each group were transferred to individual metabolic crates and habituated to breath collection harnesses for 3d before breath samples were collected daily over 6 consecutive d for CH4 emission estimation using the SF6 ‘Tracer’ technique. Sheep were then brought into respiration chambers for CH4 measurements over 4 consecutive d (‘Chamber’). During sheep occupation, chamber inlet and outlet gas streams were sampled into evacuated yokes, as for the tracer technique procedures. Samples were analysed for CH4 and SF6 mixing ratios by gas chromatography as for the Tracer technique, which were then used to estimate CH4 emissions using tracer technique procedures (i.e., Tracer in chamber). Paired t-tests based on within sheep data were used for pairwise comparisons of CH4 emission estimates between techniques. Daily CH4 emissions for the Tracer, Chamber and Tracer in chamber procedures were 14.8±2.4, 13.9±1 and 16.1±2.8g, respectively. Although Tracer and Chamber emission estimates did not differ, Tracer estimates were associated with much larger among- and within-animal variability than Chamber values, and the relationship between Chamber and Tracer estimates was poor. Rate of recovery of SF6 from chamber gases calculated by dividing the calculated daily emission of SF6 (i.e., net mixing ratio of SF6×chamber ventilation rate) by the known PR of SF6 was 10% lower than that for CH4. In sheep, the average CH4 emission estimate using the SF6 tracer technique matches that obtained from chambers, but the correlation between estimates is poor, possibly due to a mismatch in routes of excretion of tracer and trace gases.This article is part of the special issue entitled: Greenhouse Gases in Animal Agriculture – Finding a Balance between Food and Emissions, Guest Edited by T.A. McAllister, Section Guest Editors; K.A. Beauchemin, X. Hao, S. McGinn and Editor for Animal Feed Science and Technology, P.H. Robinson.
The purpose of this paper is to describe a method for determining methane emission factors for cattle. The technique involves the direct measurement of methane emissions from livestock in their natural environment. A small permeation tube containing SF[sub 6] is placed in the cow's rumen, and SF[sub 6] and CH[sub 4] concentrations are measured near the mouth and nostrils of the cow. The SF[sub 6] release provides a way to account for the dilution of gases near the animal's mouth. The CH[sub 4] emission rate can be calculated from the known SF[sub 6] emission rate and the measured SF[sub 6] and CH[sub 4] concentrations. The tracer method described provides an easy means for acquiring a large methane emissions data base from domestic livestock. The low cost and simplicity should make it possible to monitor a large number of animals in countries throughout the world. An expanded data base of this type helps to reduce uncertainty in the ruminant contribution to the global methane budget. 18 refs., 3 figs., 3 tabs.
Methane from enteric fermentation of organic matter by ruminants is considered a key contributor to climate change. This study
examined the effect of feeding a total mixed ration at different intervals, either once, twice or four times daily, on pattern
of methane emission by lactating dairy cows and developed a response function based on exponentials to describe the observed
patterns of methane emission. The function describes an asymmetrical shape exhibiting a continuous rise to a peak followed
by a period of linear decline. There were differences between treatments in terms of total methane output and the pattern
of emission, with peaks observed following feedings. The rate of decline in methane production post-prandially was linked
to amount of dry matter consumed following each feeding. The simple model fitted the data satisfactorily and provides a biological
description for fluctuations in methane release in response to changes in feeding pattern. The response function could be
applied more widely as part of methane emission inventories following further work to examine the differences in eating behaviour
and methane emission across different production systems.
Keywordsmethane–diurnal pattern–feeding frequency–dairy cows Introduction
The objectives of the present study were to compare the sulfur hexafluoride (SF₆) and respiration chamber techniques for measuring methane (CH₄) emissions from dairy cows and to determine the proportion of CH₄ that is released through the rectum. Data used were derived from 20 early lactation dairy cows in a 2 × 2 factorial design study for 4 periods with 6 wk/period. The 4 treatment diets consisted of grass silage and 2 levels of concentrate (30 and 60% dry matter basis), with or without yeast supplement. At the end of each period, CH₄ emissions were measured simultaneously using the SF₆ and respiration chamber techniques when cows were housed in chambers. The SF₆ technique was also used when cows were housed in digestibility units (barn location) before and after respiratory chamber measurements (chamber location). The simultaneous measurements in chamber location revealed that CH₄ emission estimates by the SF₆ technique were similar to those by the respiration chamber technique in the first 3 periods, although the SF₆ estimates were significantly higher in period 4. The regression of all data from the 4 periods demonstrated a linear relationship between the SF₆ and respiration chamber measurements for total CH₄ emissions (g/d, R² = 0.69) and for CH₄ emissions per unit of milk yield (g/kg, R² = 0.88), and a quadratic relationship for CH₄ emissions per unit of dry matter intake (g/kg, R² = 0.64). The CH₄ emissions from the rectum were calculated as the difference between CH₄ estimates from the SF₆ technique when cows were housed in respiratory chambers and barn locations, which was 3% of the total CH₄ emissions from the mouth, nostrils, and rectum. The SF₆ estimates in the chamber location accounted for all sources of emissions, whereas those in the barn location, like that in grazing conditions, did not include CH₄ emission from the rectum. Therefore, the SF₆ measurements for grazing cattle should be adjusted for CH₄ emissions from the rectum (3% of total). We conclude that the SF₆ technique is reasonably accurate for estimating CH₄ emissions.
1. An isotope tracer method for estimating methane production in sheep is described.
2. The technique was used to estimate methane produced in both the upper and lower digestive tract and to determine the routes by which it was excreted.
3. Four Merino ewes given lucerne chaff (33 g every hour) were used.
4. Total methane production rate was 21±1.1 ( se ) ml/min; production in the rumen accounted for 87±1.2% of the total production; 95±1.4% of the methane produced in the rumen was excreted by eructation.
5. Of the methane produced in the lower digestive tract, 89±2.3% was excreted through the lungs and 11% through the anus.
A new statistic, the Coefficient of Accuracy, C(a), has been developed by Lin for methods comparison. When an old measurement method is compared to a new measurement method or if the same method is compared in two laboratories, the Coefficient of Determination, r2, is typically used to measure the relationship. However, r2 only measures the precision of the relationship. The newly developed statistic, C(a), measures the accuracy of the relationship. When these two statistics are combined together, they form a single statistic for both accuracy and precision called the Concordance Correlation Coefficient, rc.
Two experiments were conducted to determine effects of postrumen starch infusion on milk production and energy and nitrogen utilization in lactating dairy cows. In experiment 1, four cows in early lactation fed grass silage and concentrates were continuously infused into the duodenum with water or 700, 1400, or 2100 g of purified maize starch daily for 10 to 12 d in a 4 x 4 Latin square design with 2-wk periods. Starch infusion increased milk yield linearly and decreased milk fat concentration in a quadratic manner such that increases in fat-corrected milk and calculated milk energy yield were minimal except at the highest rate of infusion. Changes in milk energy output suggest that even at the highest infusion rate metabolizable energy supplied by infused starch was used for tissue energy or oxidized. In experiment 2 energy and nitrogen balance were measured in four cows in late lactation fed a mixture of dehydrated lucerne, grass silage, and concentrates during the last 6 d of 2-wk abomasal infusions of 1200 g of purified wheat starch daily or water in a balanced switchback design with 5-wk periods. Measurements of fecal starch concentration indicated nearly all the starch infused was digested, but decreased fecal pH and apparent nitrogen digestion suggested an increase in hindgut starch fermentation. Starch infusion decreased urine nitrogen output in part because of increased tissue nitrogen retention but had no effect on milk nitrogen output. In absolute terms, numerical decreases in feed energy intake and energy digestion reduced the recovery of starch energy infused as digestible and metabolizable energy, but in terms of changes in total energy supply with starch infusion, 79% was recovered as metabolizable energy. Starch infusion had no effects on heat or milk energy but increased net energy for lactation due to a numerical increase in tissue energy, implying that in late-lactation cows, starch digested postruminally was used with high efficiency for tissue energy retention as protein and fat.
System for Measuring Metabolic Gas Emissions from Animals
- P R Zimmerman
Zimmerman, P.R., 1993. System for Measuring Metabolic Gas Emissions from Animals, U.S Patent 5265618, U.S. Patent and Trademark Office, November
30, 1993.