Comparing thermal conditions inside and outside lactating dairy cattle barns in Canada.

The health, longevity, and performance of dairy cattle can be adversely affected by heat stress. This study evaluated the in-barn condition [i.e., temperature, relative humidity, and resulting temperature-humidity index (THI)] at 9 dairy barns with various climates and farm design-management combinations. Hourly and daily indoor and outdoor conditions were compared at each farm, including both mechanically and naturally ventilated barns. On-site conditions were compared with on-farm outdoor conditions, meteorological stations up to 125 km away, and NASA Power data. Canadian dairy cattle face periods of extreme cold and periods of high THI, dependent on the regional climate and season. The northernmost location (53°N) experienced about 75% fewer hours of THI >68 compared with the southernmost location (42°N). Milking parlors had higher THI than the rest of the barn during milking times. The THI conditions inside dairy barns were well correlated with THI conditions measured outside the barns. Naturally ventilated barns with metal roofs and without sprinklers fit a linear relationship (hourly and daily means) with a slope <1, indicating that in-barn THI exceeded outdoor THI more at lower THI and reached equality at higher THI. Mechanically ventilated barns fit nonlinear relationships, which showed the in-barn THI exceeded outdoor THI more at lower THI (e.g., 55-65) and approached equality at higher THI. In-barn THI exceedance was greater in the evening and overnight due to factors such as decreased wind speed and latent heat retention. Eight regression equations were developed (4 hourly, 4 daily) to predict in-barn conditions based on outdoor conditions, considering different barn designs and management systems. Correlations between in-barn and outdoor THI were best when using the on-site weather data from the study, but publicly available weather data from stations within 50 km provided reasonable estimates. Climate stations 75 to 125 km away and NASA Power ensemble data gave poorer fit statistics. For studies involving many dairy barns, the use of NASA Power data with equations for estimating average in-barn conditions in a population is likely appropriate especially when public stations have incomplete data. Results from this study show the importance of adapting recommendation on heat stress to the barn design and guide the selection of appropriate weather data depending on the aim of the study.

Lignite effects on NH3, N2O, CO2 and CH4 emissions during composting of manure.

Production of compost from cattle manure results in ammonia (NH3) and greenhouse gas emissions, causing the loss of valuable nitrogen (N) and having negative environmental impacts. Lignite addition to cattle pens has been reported to reduce NH3 emissions from manure by approximately 60%. However, the effect of lignite additions during the manure composting process, in terms of gaseous emissions of NH3, nitrous oxide (N2O), carbon dioxide (CO2), and methane (CH4) is not clear. This composting study was conducted at a commercial cattle feedlot in Victoria, Australia. Prior to cattle entering the feedlot, we applied 4.5 kg m-2 of dry lignite to a treatment pen, and no lignite to a control pen. After 90 days of occupancy, the cattle were removed and the accumulated manure from each pen was used to form two separate compost windrows (control and treatment). During composting we collected manure samples regularly and quantified gaseous emissions of NH3, N2O, CO2, and CH4 from both windrows with an inverse-dispersion technique using open-path Fourier transform infrared spectroscopy (OP-FTIR). Over the 87-day measurement period, the cumulative gas fluxes of NH3, N2O, CO2, and CH4 were 3.4 (± 0.6, standard error), 0.4 (± 0.1), 932 (± 99), and 1.2 (± 0.3) g kg-1 (initial dry matter (DM)), respectively for the lignite amended windrow, and 7.2 (± 1.3), 0.1 (± 0.03), 579 (± 50) and -0.5 (± 0.1) g kg-1 DM, respectively for the non-lignite windrow. The addition of lignite reduced NH3 emissions by 54% during composting, but increased total greenhouse gas (GHG) emissions by 2.6 times. Total N losses as NH3-N and N2O-N were approximately 11 and 25% of initial N for the lignite and non-lignite windrows, respectively. The effectiveness of retaining N was obvious in the first three weeks after windrow formation. A cost-benefit analysis indicated that the benefit of lignite addition to cattle pens by reduced NH3 emission could justify the trade-off of increased GHG emissions.

Applicability of Eddy Covariance to Estimate Methane Emissions from Grazing Cattle.

Grazing systems represent a significant source of enteric methane (CH), but available techniques for quantifying herd scale emissions are limited. This study explores the capability of an eddy covariance (EC) measurement system for long-term monitoring of CH emissions from grazing cattle. Measurements were made in two pasture settings: in the center of a large grazing paddock, and near a watering point where animals congregated during the day. Cattle positions were monitored through time-lapse images, and this information was used with a Lagrangian stochastic dispersion model to interpret EC fluxes and derive per-animal CH emission rates. Initial grazing paddock measurements were challenged by the rapid movement of cattle across the measurement footprint, but a feed supplement placed upwind of the measurements helped retain animals within the footprint, allowing emission estimates for 20% of the recorded daytime fluxes. At the water point, >50% of the flux measurement periods included cattle emissions. Overall, cattle emissions for the paddock site were higher (253 g CH m adult equivalent [AE] d, SD = 75) and more variable than emissions at the water point (158 g CH AE d, SD = 34). Combining results from both sites gave a CH production of 0.43 g kg body weight, which is in range of other reported emissions from grazing animals. With an understanding of animal behavior to allow the most effective use of tower placement, the combination of an EC measurement platform and a Lagrangian stochastic model could have practical applications for long-term monitoring of fluxes in grazing environments.

Evaluating dispersion modeling options to estimate methane emissions from grazing beef cattle.

Enteric methane (CH) emission from cattle is a source of greenhouse gas and is an energy loss that contributes to production inefficiency for cattle. Direct measurements of enteric CH emissions are useful to quantify the magnitude and variation and to evaluate mitigation of this important greenhouse gas source. The objectives of this study were to evaluate the impact of stocking density of cattle and source configuration (i.e., point source vs. area source and elevation of area source) on CH emissions from grazing beef cattle in Queensland, Australia. This was accomplished using nonintrusive atmospheric measurements and a gas dispersion model. The average measured CH emission for the point and area source was between 240 and 250 g animal d over the entire study. There was no difference ( > 0.05) in emission when using an elevated area source (0.5 m) or a ground area source (0 m). For the point-source configuration, there was a difference in CH emission due to stocking density; likewise, some differences existed for the area-source emissions. This study demonstrates the flexibility of the area-source configuration of the dispersion model to estimate CH emissions even at a low stocking density.

Gas emissions during cattle manure composting and stockpiling.

Manure composting is a common management practice for cattle feedlots, but gaseous emissions from composting are poorly understood. The objective of this study was to quantify ammonia (NH3 ), nitrous oxide (N2 O), carbon dioxide (CO2 ), and methane (CH4 ) emissions from windrow composting (turning) and static stockpiling (nonturning) of manure at a commercial feedlot in Australia. An inverse-dispersion technique using an open-path Fourier transform infrared (OP-FTIR) spectrometer gas sensor was deployed to measure emissions of NH3 , N2 O, CO2 , and CH4 over a 165-d study period, and 29 and 15% of the total data intervals were actually used to calculate the fluxes for the windrow and stockpile, respectively. The nitrogen (N) lost as NH3 and N2 O emissions represented 26.4 and 3.8% of the initial N in windrow, and 5.3 and 0.8% of that in the stockpile, respectively. The carbon (C) lost as CO2 and CH4 emissions represented 44 and 0.3% of the initial C in windrow, and 54.8 and 0.7% of that in the stockpile, respectively. Total greenhouse gas (GHG) emissions from the manure windrow were 2.7 times higher than those of the stockpiled manure. This work highlights the value that could be accrued if one could reduce emissions of NH3 -N and N2 O-N from composting, which would retain manure N content while reducing GHG emissions.

Ammonia deposition in the neighbourhood of an intensive cattle feedlot in Victoria, Australia.

Intensive cattle feedlots are large emission sources of ammonia (NH3), but NH3 deposition to the landscape downwind of feedlots is not well understood. We conducted the first study in Australia to measure NH3 dry deposition within 1 km of a commercial beef cattle feedlot in Victoria. NH3 concentrations and deposition fluxes decreased exponentially with distance away from the feedlot. The mean NH3 concentrations decreased from 419 µg N m(-3) at 50 m to 36 µg N m(-3) at 1 km, while the mean NH3 dry deposition fluxes decreased from 2.38 µg N m(-2) s(-1) at 50 m to 0.20 µg N m(-2) s(-1) at 1 km downwind from the feedlot. These results extrapolate to NH3 deposition of 53.9 tonne N yr(-1) in the area within 1 km from the feedlot, or 67.5 kg N ha(-1) yr(-1) as an area-weighted mean, accounting for 8.1% of the annual NH3-N emissions from the feedlot. Thus NH3 deposition around feedlots is a significant nitrogen input for surrounding ecosystems. Researches need be conducted to evaluate the impacts of NH3 deposition on the surrounding natural or semi-naturals ecosystems and to reduce N fertilizer application rate for the surrounding crops by considering nitrogen input from NH3 deposition.