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TECHNICAL REPORTS

Performance of a Dispersion Model to Estimate Methane Loss from Cattle in Pens

^a Research Centre, Agriculture and Agri-Food Canada, Box 3000, Lethbridge, AB, Canada T1J 4B1
^b Dep. of Earth and Atmospheric Sciences, Univ. of Alberta, Edmonton, AB, Canada T6G 2E3

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

Received for publication December 29, 2008. Accurate measurements of enteric methane (CH₄) emissions from cattle (Bos taurus) are necessary to improve emission coefficients used in national emissions inventories, and to evaluate mitigation strategies. Our study was conducted to evaluate a novel approach that allowed near continuous CH₄ measurement from beef cattle confined in pens. The backward Lagrangian Stochastic (bLS) dispersion technique was used in conjunction with global position system (GPS) information from individual animals, to evaluate CH₄ emissions from pens of cattle. The dispersion technique was compared to estimates of CH₄ production using the SF₆ tracer technique. Sixty growing beef cattle were fed a diet containing 60% barley silage (dry matter basis) supplemented with either barley (Hordeum vulgare L.) grain or corn (Zea mays L.) distillers dried grains. The results show that daily CH₄ emissions were about 7% lower for the dispersion technique than for the tracer technique (185 vs. 199 g CH₄ animal^–1 d^–1). The precision of the dispersion technique, relative to the SF₆ tracer technique, expressed by the Pearson coefficient was 0.76; the relative accuracy given by the concordance coefficient was 0.69. The bLS dispersion technique was able to detect differences (P < 0.05) due to diet and has the added advantage of measuring the pattern of CH₄ production during the 24-h period, with emissions ranging from 161 to 279 g CH₄ animal^–1 d^–1. Configuring the cattle as point sources resulted in more accurate CH₄ emissions than assuming a uniform area release from the pen surface. The results indicate that the bLS dispersion technique using cattle as point sources can be used to accurately measure enteric CH₄ from cattle and to evaluate the impact of dietary mitigation strategies.

Abbreviations: bLS, backward Lagrangian Stochastic • DDG, drier distiller's grain • DMI, dry matter intake • GE, gross energy • GHG, greenhouse gas • GPS, global position system