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Title: Measuring the respiratory gas exchange by grazing cattle using an automated, open-circuit gas quantification system

Author
item Gunter, Stacey
item BECK, MATTHEW - Non ARS Employee

Submitted to: Translational Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/28/2017
Publication Date: 2/1/2018
Citation: Gunter, S.A., Beck, M. 2018. Measuring the respiratory gas exchange by grazing cattle using an automated, open-circuit gas quantification system. Translational Animal Science. 2:11-18. https://doi.org/doi:10.1093/tas/txx009.
DOI: https://doi.org/10.1093/tas/txx009

Interpretive Summary: Ruminants are a source of enteric methane, which has been identified as a greenhouse gas that contributes to climate change. With interest in developing technologies to decrease enteric methane emission, systems are currently being developed to measure the methane emission by cattle. An issue with grazing cattle is the ability to measure methane emissions in open-air environments. A scientific instrument for this task is the GreenFeed emission monitoring (GEM) system (C-Lock, Inc.; Rapid City, SD). The GEM system is a head-chamber that grazing cattle occasionally visit and while the animal consumes a small portion of bait (3 to 8 minute), the GEM captures the animal’s breath cloud by exhausting air through the GEM system. The breath cloud is then analyzed for methane, carbon dioxide, and oxygen concentrations. Data are hourly uploaded to a server where it is processed using algorithms to determine total daily fluxes. Several factors affect the emission estimates generated by the GEM systems including the animal’s visitation rate, length of sampling period, and airflow through the system. The location of the GEM is an important factor in determining the cattle’s willingness to visit. Further, cattle need to be trained to use the GEM system, which normally requires 4 to 8 weeks. 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 GEM system, the bait delivery rate has little effect on the animal’s willingness to use the system. Airflow through the GEM is an important factor, but as long as airflow is maintained above 26 liters/second the breath-cloud capture seems complete. There is great concern regarding circadian variation in the instantaneous production rates of methane because the GEM system only spot-samples 3 to 4 times/day. Preliminary analysis has shown variation in the instantaneous production rates of methane do not vary as greatly with grazing cattle compared to meal-fed cattle. It seems that increasing the visitation length decreases variation in emission estimated, but there is a diminishing return to increasing visitation length. The GEM system is a useful tool for researching the nutrition and emissions of grazing cattle, but great care must be taken to obtain and use the best quality data possible.

Technical Abstract: Ruminants are a source of enteric methane (CH4), which has been identified as a greenhouse gas that contributes to climate change. With interest in developing technologies to decrease enteric CH4 emission, systems are currently being developed to measure the CH4 emission 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 the GreenFeed emission monitoring (GEM) system (C-Lock, Inc.; Rapid City, SD). The GEM system is a head-chamber that grazing cattle occasionally visit and while the animal consumes a small portion of bait (3 to 8 minute), the GEM captures the animal’s breath cloud by exhausting air through the GEM system. The breath cloud is then analyzed for CH4, carbon dioxide, and oxygen concentrations. Data are hourly uploaded to a server where it is processed using algorithms to determine total daily fluxes. Several factors affect the emission estimates generated by the GEM systems including the animal’s visitation rate, length of sampling period, and airflow through the system. The location of the GEM is an important factor in determining the cattle’s willingness to visit. Further, cattle need to be trained to use the GEM system, which normally requires 4 to 8 weeks. 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 GEM system, the bait delivery rate has little effect on the animal’s willingness to use the system. Airflow through the GEM is an important factor, but as long as airflow is maintained above 26 liters/second the breath-cloud capture seems complete. There is great concern regarding circadian variation in the instantaneous production rates of CH4 because the GEM system only spot-samples 3 to 4 times/day. 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 emission estimated, but there is a diminishing return to increasing visitation length. The GEM system is a useful tool for researching the nutrition and emissions of grazing cattle, but great care must be taken to obtain and use the best quality data possible.