Moving Toward Sustainability: Challenges in Greenhouse Gas (GHG) Monitoring in Grazing Systems

Greenhouse gases (GHG) emitted by cattle, particularly enteric methane (CH4) emissions, are a significant contributor to global warming, accounting for 27% of U.S. CH4 emissions (EPA, 2024). In the United States, 36% of land is used for cattle grazing systems, grazing cattle contribute to 75% of the CH4 from the beef cattle life cycle. Accurately measuring CH4 emissions from these systems is crucial to improving our ability to develop effective strategies to reduce emissions. However, researchers at AgNext find that measuring enteric CH4 emissions in grazing systems is challenging due to several factors: 

Acclimating to GreenFeed units: Automated head chamber systems or GreenFeed systems (C-Lock Inc., Rapid City, SD) are designed to measure GHG emissions from ruminants as they eat pellets dispensed by the machine. However, training grazing animals to use these machines is challenging. Animals in feedlot pens, which are confined to pens fed from a bunk on a more regular schedule, can be trained to utilize the system more frequently. Grazing animals roam large areas of rangelands, making it harder for them to learn and consistently use the GreenFeed systems.  

Frequency of Visits: For accurate enteric CH4 measurements, each animal ideally needs to visit the Greenfeed system 35 times or more throughout the experimental period. Frequent visits are essential to capture the variability in CH4 emissions from ruminants throughout the day. Methane emissions can fluctuate significantly due to factors such as digestion cycles, activity levels, and changes in body weight, dry matter intake (DMI), and diet quality (which can vary with pasture quality throughout the seasons). Therefore, having multiple visits spread throughout the day and across the experimental period ensures a more comprehensive and accurate measurement of CH4 emissions. Grazing animals typically move in herds across expansive pastures, making it challenging to ensure that every animal visits the machine regularly. Researchers at AgNext have often placed GreenFeed systems near the pasture’s water tank, assuming animals will visit these areas daily. However, animals may not always choose to visit, especially when natural water sources are available in the pasture. 

Measuring Dry Matter Intake (DMI): Knowing the amount of dry matter that the animals consume is crucial for calculating CH4 yield (CH4 emitted per kg of dry matter consumed). In grazing systems, where animals can be dispersed over large areas, accurately measuring DMI is often inaccurate, labor-intensive, and expensive. Current methods, such as estimating the forage before and after the animals consume it or using external markers and collecting the animal’s feces, are not always feasible or accurate for extensive grazing operations. 

Diet Quality Impact: The pellets used as bait in GreenFeed systems can alter animals’ diets. Each animal can consume up to 2 pounds of pellets per day. This consumption can affect the nutritional balance of their overall diet, especially since pasture quality may be different than the characteristics of the pellets. Pasture quality varies seasonally and across different regions. Different plant species can dominate pastures seasonally, influencing the nutritional content and influencing the CH4 emissions produced by grazing animals. 

Animal using GreenFeed at the Central Plains Experimental Range (CPER). The GreenFeed machines are strategically placed near the water tank to increase usage by the grazing animals.

Despite these challenges, measuring enteric CH4 emissions in grazing systems is essential and something AgNext centers in our research. It provides valuable data on the environmental impact of livestock production, particularly in regions where grazing is the predominant method of raising animals. By understanding the factors that can influence enteric CH4 emissions and developing mitigation strategies, such as improving grazing management practices or altering diet compositions, producers can work towards reducing the overall carbon footprint of livestock agriculture. 

Efforts are underway to improve measurement techniques and overcome these challenges. AgNext researchers are exploring new technologies, such as remote sensing and virtual fences, to understand the animal’s behavior better and potentially implement management practices. The overall goal is to improve enteric CH4 measurement and reduce enteric CH4 emissions in grazing systems. Collaborative efforts between scientists, farmers, and policymakers are essential to developing practical solutions that balance environmental sustainability with the need to feed a growing global population. 

In conclusion, while measuring enteric CH4 emissions in grazing systems presents numerous challenges, it is a critical effort for mitigating the environmental impact of livestock production. Continued research and innovation are necessary to overcome these challenges and develop sustainable agricultural practices that support both ecological health and food security. 

Picture of Inés Mesa

Inés Mesa

Graduate Student