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TECHNICAL REPORTS

Assessment of the Sulfur Hexafluoride (SF₆) Tracer Technique for Measuring Enteric Methane Emissions from Cattle

^a Agriculture and Agri-Food Canada, P.O. Box 3000, Lethbridge, AB, Canada T1J 4B1
^b Agriculture and Agri-Food Canada, Swift Current, SK, Canada S9H 3X2

^* Corresponding author (mcginns{at}agr.gc.ca)

Received for publication February 7, 2006. A commonly used method of measuring enteric methane (CH₄) emissions from ruminants is the SF₆ tracer technique that measures respired and eructated CH₄. However, within the animal, a small proportion of CH₄ is produced post-ruminally and some of this may escape through the rectum. The comparison of emissions using a chamber technique that measures all enteric CH₄ losses, and the SF₆ tracer technique, could give some insight into the magnitude of post-ruminal emission. The objective of our study was to assess the precision and accuracy of the SF₆ tracer technique against a chamber technique for cattle fed a range of diets. Using a repeated-measures design, eight beef heifers were offered a high grain or high forage diet for ad libitum or restricted (65% of ad libitum) feed intake to vary the site of digestion within the gastrointestinal tract (n = 24). The SF₆ tracer technique underestimated CH₄ emissions on average by 4% relative to the chamber technique. This difference was not significant (P > 0.05) and suggests low post-ruminal CH₄ emissions. There was a trend for greater accuracy and precision of the SF₆ tracer technique when used with cattle fed a high forage diet at a restricted level of intake. The high forage diet corresponds to the conditions of cattle grazing pasture, suggesting the SF₆ tracer technique is most reliable for the grazing system.

Abbreviations: DM, dry matter • ERUCT, Emissions from Ruminants using a Calibrated Tracer • GC, gas chromatography

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