Effect of release rate of the SF6 tracer on methane emission estimates based on ruminal and breath gas samples

Abstract

The release rate (RR) of sulphur hexafluoride (SF 6 ) gas from permeation tube in the rumen appears to be positively related with methane (CH 4 ) emissions calculated using the SF 6 tracer technique. Gas samples of breath and ruminal headspace were collected simultaneously in order to evaluate the hypothesis that transactions of SF 6 in the rumen are the source for this relationship. Six non-lactating dairy cows fitted with rumen cannulae were subdivided into two groups and randomly assigned to a two-period crossover design to permeation tubes with low RR (LRR 5 1.577 mg/day) or two-times higher RR (HRR 5 3.147 mg/day) RR. The cows were fed limited amounts of maize silage (80% ad libitum) split into two meals (40% at 0800 h and 60% at 1600 h). Each period consisted of 3-day gas sampling. Immediately before the morning feed and then each hour over 8 h, ruminal gas samples (50 ml) were withdrawn through the cannula fitted with stoppers to prevent opening. Simultaneously, 8-h integrated breath gas samples were collected over the same period. Ratios of concentration of CH 4 /SF 6 , CO 2 /SF 6 and CO 2 /CH 4 and emission estimates of CH 4 and CO 2 were calculated for each sample source using the SF 6 tracer technique principles. The LRR treatment yielded higher (P , 0.001) ruminal CH 4 /SF 6 (by 1.79 times) and CO 2 /SF 6 (by 1.90 times) ratios than the HRR treatment; however, these differences were lower than the 2.0 times difference expected from the RR between the LRR and HRR. Consequently, the LRR treatment was associated with lower (P , 0.01) ruminal emissions of CH 4 over the 8-h collection period than with the HRR treatment (111%), a difference also confirmed by the breath samples (111%). RR treatments did not differ (P 5 0.53) in ruminal or breath CO 2 emissions; however, our results confirm that the SF 6 tracer seems inappropriate for CO 2 emissions estimation in ruminants. Irrespective of the RR treatment, breath samples yielded 8% to 9% higher CH 4 emission estimates than the ruminal samples (P 5 0.01). The relationship between rumen and breath sources for CH 4 emissions was better for LRR than for HRR treatment, suggesting that tracer performance decreases with the highest RR of SF 6 tested in our study (3.1 mg/day). A hypothesis is discussed with regard to the mechanism responsible for the relationship between RR and CH 4 emission estimates. The use of permeation tubes with small range in RR is recommended in animal experiments to decrease variability in CH 4 emission estimates using the SF 6 tracer technique.Keywords: SF 6 tracer, permeation rate, methane, breath, ruminal gas ImplicationsThe sulphur hexafluoride (SF 6 ) tracer technique is a method of choice to estimate individual methane (CH 4 ) emissions from large groups of animals under production conditions such as grazing. However, the CH 4 emissions estimates appear related to the SF 6 release rate (RR) in the rumen. This suggests the need to use permeation tubes with a small range in RR in animal experiments, and that the RR is balanced across t...

Effect of Origanum vulgare L. leaves on rumen fermentation, production, and milk fatty acid composition in lactating dairy cows

“…Comparison of breath versus rumen headspace gas sampling for estimation of rumen methane production when using the SF 6 technique has not often been performed. In one such comparison, Martin et al (2010) reported similar methane-emission rates between the 2 methods. The effect of cannula leakage on the accuracy of methane emission measurement has not been thoroughly investigated.…”

Trimethylamine emissions in animal husbandry

“…Like NH 3 , TMA diffuses through the rumen wall into plasma and blood stream (Bain et al, 2005). In the liver, the NH 3 is converted to urea as a detoxification mechanism (Meijer et al, 1990;Walt, 1993). Similarly, TMA acts detrimentally (Guest and Varma, 1992;Rappert and Müller, 2005) while liver cells are capable of enzymatically oxidising TMA to TMAO (Baker and Chaykin, 1962;Baker et al, 1963;Gut and Conney, 1993;Bennett et al, 2013).…”

Effect of Rice Wine Distillers By-Product on Digestibility and Nitrogen Retention in Pre-Pregnant Bach Thao Goats

“…The correlation between emission values obtained from individual animals and repeatability in the estimated rates was also low for the SF 6 method (Clark, 2010;Pinares-Patiño et al, 2010). Various factors, including permeation rate (Pinares-Patiño and Clark, 2008;Martin et al, 2010b), retention of the tracer in the digestive tract (Lassey et al, 2011), and different behaviour of tracer vs tracee gases (Pinares-Patiño et al, 2010) may affect CH 4 emission measurements with the SF 6 technique. In vitro gas production systems have been modified to measure CH 4 (Pellikaan et al, 2011a;Navarro-Villa et al, 2011), but they suffer from the same disadvantages as all in vitro techniques (see previous discussion).…”