Post-experiment correction for release rate in permeation tubes improves the accuracy of the sulphur hexafluoride (SF₆) tracer technique in deer

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• 作者：N.M. Swainson^a ; ^b ; ^{natasha.swainson@agresearch.co.nz"" rel=""nofollow} ; I.M. Brookes^a ; S.O. Hoskin^a ; ^b ; H. Clark^c
• 关键词：Methane ; Sulphur hexafluoride technique ; SF₆ release rate ; Permeation tube
• 刊名：Animal Feed Science and Technology
• 出版年：2011
• 出版时间：23 June 2011
• 年：2011
• 卷：166-167
• 期：Complete
• 页码：192-197
• 全文大小：214 K

文摘

The sulphur hexafluoride (SF6) tracer technique is a means to estimate CH₄ emissions from individual ruminants, particularly whilst grazing. The success of the SF₆ technique is reliant upon accurate determination of the release rate of SF₆ gas from the permeation tubes (PT). Our study aimed to determine effects of SF₆ PT rumen residence time on the release rate of SF₆ gas and calculated CH₄ production (as g CH₄/d) in grazing red deer. The CH₄ emissions of red deer stags grazing permanent perennial ryegrass based pasture were estimated daily for 5 d at 4.5, 6.5, 9.0 and 11.5 months of age, corresponding to a PT release period of 55, 111, 195 and 258 d. Permeation tube charge time refers to the number of days since PT were charged with SF₆. The PT were recovered from 3 deer after the second CH₄ measurement and from the remaining 10 deer at the end of the experiment. Release rates of SF₆ gas from PT were determined pre-insertion to the rumen (i.e., uncorrected SF₆ release rates), or by pre-insertion SF₆ release rate with adjustment for SF₆ release rates from PT recovered at the termination of the experiment (i.e., corrected SF₆ release rates), after the PT had resided in the rumen of red deer for 212 d. A difference of 12.8 % between corrected and uncorrected SF₆ release rates (P=0.07) occurred after 9 d of PT rumen residence. In contrast, after 65, 150 and 212 d of PT residence, corrected release rates were lower (P<0.05) than uncorrected SF₆ release rates by 16, 19.5 and 27 % , respectively. Calculated CH₄ production and yield (as g CH₄/kg dry matter intake) of deer was also reduced by up to 15 % (P<0.001) when calculated using corrected versus uncorrected SF₆ release rates. Results imply that use of uncorrected SF₆ release rates may not be representative of actual SF₆ release rate from PT whilst they reside in the rumen. Results also suggest that PT should be recovered upon completion of the experiment and SF₆ release rates estimated in order to improve accuracy of calculated CH₄ emissions.

This paper is part of the special issue entitled: Greenhouse Gases in Animal Agriculture – Finding a Balance between Food and Emissions, Guest Edited by T.A. McAllister, Section Guest Editors: K.A. Beauchemin, X. Hao, S. McGinn and Editor for Animal Feed Science and Technology, P.H. Robinson.