On the use of SF6 technique in Latin America for measuring methane emissions in ruminants.

GERE J. I.; CERÓN CUCCHI M.E.; GUALDRÓN-DUARTE, LAURA BIBIANA; TIERI M.P.; LOZA C.; HUANCA N.; ORELLANAS G.; VELÉZ V.; CABEZAS E.

Conferencia; 8th Greenhouse Gas and Animal Agriculture Conference.; 2022

The sulfur hexafluoride (SF6) gas-tracer technique is especially useful for measuring CH4 methane emissions in ruminants under grazing conditions and it has been used for in Latin America for conducting scientific research, primarily nutritional evaluations. Although guidelines on how to properly implement this technique have been published, the use of the SF6 method is still often criticized due to a greater variation within measurements, when compared to results obtained either from respiration chambers or by the GreenFeed method. This may suggest that detailed evaluation of the SF6 technique is worth conducting in order to identify the main sources of variability and minimize inconsistencies. The aim of this study was to provide a summary of key variables in this matter, reported in studies with the SF6 technique conducted in Latin America. Data were obtained by searching a wide range of databases, and only papers published in English language peer-reviewed journals were considered for analysis. The final database comprised 63 studies, of which 38 were in grazing systems and the rest were in confinement. The categories evaluated were: beef cattle (40); dairy cattle (14); and small ruminants (9). The variables considered were: i) the duration of collection period (12h = 3%; 24h = 68%; 5 days = 29%); ii) the collection vessel (PVC yokes = 68% and stainless-steel cylinders = 29%); iii) inflow restrictor type (capillary = 65% and ball bearing system = 24%); and iv) the mean permeation rate of the SF6 tubes, in mg/day (< 2 = 17%; 2 to 5 = 44% and > 5 = 10%). Additionally, calibration times reported were within 4 to 17 weeks. The minimum time between the insertion of the SF6 tubes into the rumen and the beginning of the measurement period was 3 days, while the maximum was 21 days. Overall, it is concluded that studies like these are important to identify weaknesses and complement efforts among research institutions in Latin America to get more reliable results when using the SF6 tracer technique.