The SF6 Tracer Technique: Methane Measurement From Ruminants

DOI: 10.1007/978-1-4020-6133-2_3 In book: Measuring Methane Production From Ruminants, pp.33-67

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    • "The calibration curves were constructed, using gas standards certified by White Martins (Praxair Inc), as described by Westberg et al. (1998). The flow rate of CH 4 released by the animal was calculated in relation to the flow of SF 6 , correlating the results with the known release rate of SF 6 in the rumen, subtracted from baseline CH 4 concentrations (Westberg et al., 1998): Q CH4 = Q SF6 × ([CH 4 ] Y − [CH 4 ] B )/[SF 6 ], in which Q CH4 = emission rate of CH 4 by the animal; Q SF6 = known release rate of SF6; [CH 4 ] Y = concentration of CH 4 in the canister; [CH 4 ] B = concentration of CH 4 in the blank; and [SF 6 ] = concentration of sulfur hexafluoride in the canister. The equation of Blaxter and Clapperton (1965), corrected by Wilkerson et al. (1995), was used to calculate the loss of gross energy in the form of methane: CH 4 /GEI = [(CH 4 × 0.0133)/GEI] × 100, in which GEI is the gross energy intake and 0.0133 is the gross energy in Mcal/g CH 4 (Holter and Young, 1992). "
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    ABSTRACT: Feed intake and average daily gain (ADG) in Nellore cattle were determined to calculate residual feed intake in two performance tests: first during the growth phase (RFIgrowth) and then during a measurement of the methane emission phase (RFImet). During the RFIgrowth test, 62 males and 56 females were classified as low-, medium-, and high-RFI. Enteric methane emission was measured in 46 animals; 23 males used for RFImet measurement plus 23 females (22 low-RFIgrowth and 24 high-RFIgrowth). Diet consisted of Brachiaria brizantha cv. Marandu hay (445 g/kg DM) and concentrate (555 g/kg DM). During the RFIgrowth and RFImet phases, DMI was lower in the animals with low RFI, with no difference in ADG. Residual feed intake was -0.359 and 0.367 kg DM/d for low- and high-RFI animals. Enteric methane emission (g/d, g/kg BW0.75 and g/kg ADG) did not differ between RFIgrowth classes. Enteric methane emission (g/d) was higher in high RFImet and lower in low RFImet males. Spearman correlations among traits obtained during both tests, which were high between metabolic BW (r = 0.959) and between DMI (r = 0.718), and zero between ADG (r = -0.062), resulted in moderate correlation between RFIgrowth and RFImet (r = 0.412). However, it is not possible to confirm that high-efficiency animals release less enteric methane, since different results were obtained when enteric methane was compared between the RFIgrowth and RFImet classes.
    Full-text · Article · Jul 2015
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    • "La medición de las emisiones de metano (CH 4 ) de rumiantes se realiza, generalmente, utilizando la técnica del trazador hexafluoruro de azufre (SF 6 ) originalmente desarrollada por Johnson y Johnson (1995). Esta técnica permite la cuantificación diaria de CH 4 por animal y es internacionalmente reconocida como la más apropiada para medir las emisiones de metano en sistemas de pastoreo en virtud que los equipos se instalan sobre el animal sin impedir ni limitar sus movimientos ni sus hábitos en la pastura (Johnson et al., 2007; Lassey et al., 1997; Woodward et al., 2004; Grainger et al., 2007). La utilización del SF 6 responde a que es un gas considerado como el mejor trazador para medir la cantidad de metano emitido por los rumiantes, debido a que posee una elevada estabilidad en el rumen de los animales, inclusive superior a la de gases isótopos del metano. "

    Full-text · Technical Report · Mar 2015
    • "Canisters with samples were then over-pressurized with nitrogen (N 2 ) gas to approximately 162 kPa and a subsample from each canister was transferred to a glass vial (22 mL), previous to gas concentration analysis. For measuring background SF 6 and CH 4 gases, two types of background collectors were used, the traditional fixed background collectors (Johnson et al., 2007) and mobile background collectors (Berndt et al., 2014). Two fixed canisters, one per treatment, located outside the grazing sub-paddocks were used as fixed background collectors. "
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    ABSTRACT: Although concentrate supplements in ruminant diets have been recognised as an effective enteric methane mitigation strategy, very few studies have examined the effects of concentrate supplementation on enteric methane emissions under grazing conditions. Twenty four multiparous Holstein Friesian cows were used in a crossover design study to investigate the effects of two concentrate feeding levels across two periods on enteric methane emission and milk production of grazing dairy cows. Each period had a duration of four weeks (three weeks for diet adaptation and one week for measurements) and no interval in between them. Dietary treatments consisted of 2 concentrate feeding levels per cow (1 vs. 5 kg; as-fed basis) offered daily in equal meals during milking. Enteric methane emissions from cows grazing perennial ryegrass pasture were measured during the final week of each period using the sulphur hexafluoride tracer technique. Milk yield and liveweight were determined daily during each methane measurement period, whereas milk composition and body condition score (BCS) were determined weekly. Daily herbage intake by individual cows during methane measurement weeks was estimated using an energy requirement model and animal records and diet composition. In period 1, cows receiving 5 kg concentrate supplement were estimated to reduce herbage intake by 1.8 kg DM/d compared to cows receiving 1 kg of concentrate, whereas in period 2 cows receiving the 5 kg concentrate supplementation were estimated to reduce herbage intake by 4.4 kg DM/d, compared to cows receiving 1 kg of concentrate. In both periods, milk yield increased with increasing concentrate level, with an average milk response to concentrate supplementation of 0.68 kg milk DM / kg concentrate DM over the two periods. Concentrate feeding level had no effect on milk fat, protein or total solids contents. In period 2, lactose content increased in cows offered 5 kg/d concentrate. Increasing concentrate feeding level increased liveweight and BCS in period 1, but not in period 2. Feeding 5 kg of concentrate supplement increased enteric methane emission by 34 g/d in period 1 (323 vs. 357 g/d) and 41 g/d in period 2 (349 vs. 390 g/d) compared to 1 kg of concentrate supplement. However, enteric methane emission per unit of estimated feed intake (dry matter or gross energy) or milk output (gross or energy corrected) was not affected by level of concentrate supplementation. It was concluded that under generous grazing conditions (high allowance of good quality herbage) a moderate increase in concentrate supplementation resulted in a simultaneous increase in milk yield and enteric methane emission, so that enteric methane emission per unit of milk yield was unaffected. Thus, a moderate level of concentrate supplementation of dairy cows grazing pastures of high digestibility would not be an effective enteric methane mitigation strategy.
    No preview · Article · Feb 2015 · Livestock Science
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