Methane emissions from cattle: Estimates from short-term measurements using a GreenFeed system compared with measurements obtained using respiration chambers or sulphur hexafluoride tracer

Abstract

a b s t r a c tThe GreenFeed (GF) system (C-Lock Inc., Rapid City, USA) is used to estimate total daily methane emissions of individual cattle using short-term measurements obtained over several days. Our objective was to compare measurements of methane emission by growing cattle obtained using the GF system with measurements using respiration chambers (RC) or sulphur hexafluoride tracer (SF 6 ). It was hypothesised that estimates of methane emission for individual animals and treatments would be similar for GF compared to RC or SF 6 techniques. In experiment 1, maize or grass silage-based diets were fed to four growing Holstein heifers, whilst for experiment 2, four different heifers were fed four haylage treatments. Both experiments were a 4 × 4 Latin square design with 33 day periods. GreenFeed measurements of methane emission were obtained over 7 days (days 22-28) and compared to subsequent RC measurements over 4 days (days 29-33). For experiment 3, 12 growing heifers rotationally grazed three swards for 26 days, with simultaneous GF and SF 6 measurements over two 4 day measurement periods (days 15-19 and days 22-26). Overall methane emissions (g/day and g/kg dry matter intake [DMI]) measured using GF in experiments 1 (198 and 26.6, respectively) and 2 (208 and 27.8, respectively) were similar to averages obtained using RC (218 and 28.3, respectively for experiment 1; and 209 and 27.7, respectively, for experiment 2); but there was poor concordance between the two methods (0.1043 for experiments 1 and 2 combined). Overall, methane emissions measured using SF 6 were higher (P<0.001) than GF during grazing (186 vs. 164 g/day), but there was significant (P<0.01) concordance between the two methods (0.6017). There were fewer methane measurements by GF under grazing conditions in experiment 3 (1.60/day) compared to indoor measurements in experiments 1 (2.11/day) and 2 (2.34/day). Significant treatment effects on methane emission measured using RC and SF 6 were not evident for GF measurements, and the ranking for treatments and individual animals differed using the GF system. We conclude that under our conditions of use the GF system was unable to detect significant treatment and individual animal differences in methane emissions that were Abbreviations: CI, confidence interval; DM(I), dry matter (intake); GF, GreenFeed; LW, live weight; LWG, LW gain; NDIR, non-dispersive infrared; RC, respiration chambers; RFID, radio frequency identification; SF6, sulphur hexafluoride tracer. identified using both RC and SF 6 techniques, in part due to limited numbers and timing of measurements obtained. Our data suggest that successful use of the GF system is reliant on the number and timing of measurements obtained relative to diurnal patterns of methane emission.

Review of current in vivo measurement techniques for quantifying enteric methane emission from ruminants

“…The GreenFeed system has been reported by Hammond et al (2015) to provide an overall estimate of CH 4 emission by growing dairy cattle that was not different from measurements made in respiration chambers (n = 8) but lower than the values obtained using the SF 6 technique (n = 12; Table 1). Dorich et al (2015) found average CH 4 emission from lactating dairy cows (n =16) measured using the GreenFeed and SF 6 technique were similar, but the SF 6 technique showed higher variability in the relationship between CH 4 (g/d) and DMI (r 2 = 0.17, P < 0.02), compared with GreenFeed (r 2 = 0.42, P < 0.01).…”

“…On pasture or in a free-stall facility, successful use of the GreenFeed system is reliant on animal visitation to the unit, and, for some, the number and timing of CH 4 measurements obtained relative to diurnal patterns of CH 4 emission may not be truly representative of daily fluctuations in CH 4 emission (Renand et al, 2013;Hammond et al, 2015). In a trial with young beef bulls (n = 18) fed pellet diets, Renand et al (2013) reported that CH 4 emission estimated with GreenFeed was significantly higher during the day (263 g/d from 08:00 to 16:00 h) than at night (216 g/d from 00:00 to 08:00 h).…”

“…Amounts fed depend on the enticement used and the intended duration of visit. Supplemental feed may be a concern in both pastoral grazing systems and animal nutrition studies where there is the possibility of an excessive contribution of enticement feed to the diet, even if restrictions are imposed (Waghorn et al, 2013;Dorich et al, 2015;Hammond et al, 2015).…”

“…Compared with respiration chamber and SF 6 techniques, it will take more time and more animals to undertake a treatment comparison on CH 4 emission using GreenFeed with voluntary visitation if some animals avoid the GreenFeed unit or do not visit it each day in a free-stall barn or pasture environments (Hammond et al, 2015). Cottle et al (2015) assessed the duration and number of GreenFeed measurements required for estimating daily CH 4…”

Reducing the carbon footprint of Australian milk production by mitigation of enteric methane emissions

“…Velazco et al (2014) concluded that there was a need for caution in extrapolating 'short-term emission measures', as are obtained by the GreenFeed system, to daily methane-emission rates. This need for caution when employing the GreenFeed system was also recently echoed by Hammond et al (2015). Hammond et al (2015) conducted two experiments in which Holstein heifers were fed various diets, and one experiment in which growing heifers rotationally grazed swards of either ryegrass, clover or flowers.…”