Short communication: Use of a portable, automated, open-circuit gas quantification system and the sulfur hexafluoride tracer technique for measuring enteric methane emissions in Holstein cows fed ad libitum or restricted

Abstract

The objective of this study was to measure enteric CH4 emissions using a new portable automated open-circuit gas quantification system (GQS) and the sulfur hexafluoride tracer technique (SF6) in midlactation Holstein cows housed in a tiestall barn. Sixteen cows averaging 176 ± 34 d in milk, 40.7 ± 6.1 kg of milk yield, and 685 ± 49 kg of body weight were randomly assigned to 1 out of 2 treatments according to a crossover design. Treatments were (1) ad libitum (adjusted daily to yield 10% orts) and (2) restricted feed intake [set to restrict feed by 10% of baseline dry matter intake (DMI)]. Each experimental period lasted 22d, with 14 d for treatment adaptation and 8d for data and sample collection. A common diet was fed to the cows as a total mixed ration and contained 40.4% corn silage, 11.2% grass-legume haylage, and 48.4% concentrate on a dry matter basis. Spot 5-min measurements using the GQS were taken twice daily with a 12-h interval between sampling and sampling times advanced 2h daily to account for diurnal variation in CH4 emissions. Canisters for the SF6 method were sampled twice daily before milking with 4 local background gas canisters inside the barn analyzed for background gas concentrations. Enteric CH4 emissions were not affected by treatments and averaged 472 and 458 g/d (standard error of the mean = 18 g/d) for ad libitum and restricted intake treatments, respectively (data not shown). The GQS appears to be a reliable method because of the relatively low coefficients of variation (ranging from 14.1 to 22.4%) for CH4 emissions and a moderate relationship (coefficient of determination = 0.42) between CH4 emissions and DMI. The SF6 resulted in large coefficients of variation (ranging from 16.0 to 111%) for CH4 emissions and a poor relationship (coefficient of determination = 0.17) between CH4 emissions and DMI, likely because of limited barn ventilation and high background gas concentration. Research with improved barn ventilation systems or outdoors is warranted to further assess the GQS and SF6 methodologies.

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

“…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). The authors attributed this higher variability for SF 6 measurements to the high concentration of background gases combined with poor barn ventilation.…”

“…The authors concluded that the visit hours had a significant effect on estimated CH 4 emission, particularly for animals whose number of visits were low and irregular during the day. Methane emission may be biased by sampling times; generally being highest after feeding and during rumination bouts (Storm et al, 2012;Hegarty, 2013;Dorich et al, 2015;Hristov et al, 2015b). As explained in Branco et al (2015) and Hristov et al (2015a, b), best results with GreenFeed are obtained when the number and timing of animal visits are controlled by the investigator, which is easily achievable in a tie-stall barn situation.…”

“…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).…”

The Use of an Automated System (GreenFeed) to Monitor Enteric Methane and Carbon Dioxide Emissions from Ruminant Animals

“…In a study with lactating dairy cows, it was concluded that CH 4 emissions measured by the AHCS were similar to literature values derived from respiration chambers and between animal variability (CV of 11 to 12%; repeatability of 0.64 to 0.81) was also within the range reported for respiration chambers 10 . In a recently-published study with lactating cows, AHCS produced a smaller CV than the SF 6 method (14.1 to 22.4% vs. 16.0 to 111% for SF 6 ) 13 . In a 12-week experiment conducted at the Pennsylvania State University with 48 lactating dairy cows, in which rumen CH 4 production was inhibited by 30% (P < 0.001), we concluded that AHCS and the SF 6 method produced similar CH 4 emission results: 319 to 481 g/cow per day (mean = 374 g/d; SEM = 15.9; CV = 13%) and 345 to 485 g/cow per day (mean = 396 g/d; SEM = 29.8; CV = 23%) for AHCS and SF 6 , respectively 14 .…”

Starch and dextrose at 2 levels of rumen-degradable protein in iso-nitrogenous diets: Effects on lactation performance, ruminal measurements, methane emission, digestibility, and nitrogen balance of dairy cows

“…In the cow selection phase of the study, a group of 24 multiparous Holstein dairy cows housed in tiestalls were adapted to the GreenFeed unit (C-Lock Inc., Rapid City, SD) that quantifies CH 4 production with minimal disturbance (Dorich et al, 2015). Adaptation was measured once daily for 7 d with a score (on a scale of 1 to 5) reflecting a cow's willingness to move her head forward and keep it in the hooded trough area of the GreenFeed unit when enticed with small amounts of concentrates offered over a 5-min period.…”