Comparison of three techniques for measuring enteric methane emissions by ruminants

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Arbre, Marie | Martin, Cécile | Rochette, Yvanne | Lascoux, Clothilde | Eugène, Maguy | Doreau, Michel, M.

Edité par CCSD ; Academic Publishers -

Session 54 : Poster 8. International audience. The open-circuit chamber (OC), the SF6 tracer technique (SF6) and the GreenFeed system (GF) are three techniques for measuring enteric methane (CH4) emissions by ruminants. These methods estimate individual daily CH4 emissions, from eructed and expired gas samples collected either continuously over 24 h, in a canister for SF6 and in chamber for OC, or several times a day during short-term periods (3-8 min) when cattle visit an automated feeder fitted with a head chamber for GF. The objective of this work is to compare these three techniques during a 46-day period. Methane emissions were measured on 8 dry cows fed the same diet (70% hay + 30% concentrate) in restricted amounts, constant among cows throughout the experiment: 13.3±0.5 kg/day dry matter intake (DMI). Measurements in OC were performed twice for 4 days at 3-week interval, and SF6 technique was performed in free-stalls barn (SF6-FS) twice for 4 days at 3-week interval and once for 4 days in chambers (SF6-C). GreenFeed was used continuously for 30 days and data were split in two 15-day periods. Data were analyzed using PROC MIXED of SAS. Methane emissions in g/kg DMI averaged for the two periods: 24.2±4.9 for SF6-FS, 27.7±3.3 for OC and 23.7±3.3 for GF. Analyses of variance showed an effect of techniques, OC resulting in higher CH4 emissions in g/kg DMI than the two other techniques (P<0.001). Neither an effect of period nor a technique × period interaction was shown (P>0.05). Emissions using SF6 in chambers (SF6-C) were 23.7±2.4 g/kg DMI. The difference between CH4 measurement techniques can be explained in part because GF and SF6 record only eructed and expired gases whereas OC records in addition gases from flatulence and CH4 from feces fermentation. Pearson correlation coefficients for individual methane emissions (n=8) were 0.80, 0.85, 0.30 and 0.37 between OC and SF6-FS, OC and SF6-C, OC and GF, SF6-FS and GF, respectively.

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