Comparison of the sulfur hexafluoride tracer and respiration chamber techniques for estimating methane emissions and correction for rectum methane output from dairy cows

Abstract

The objectives of the present study were to compare the sulfur hexafluoride (SF₆) and respiration chamber techniques for measuring methane (CH₄) emissions from dairy cows and to determine the proportion of CH₄ that is released through the rectum. Data used were derived from 20 early lactation dairy cows in a 2 × 2 factorial design study for 4 periods with 6 wk/period. The 4 treatment diets consisted of grass silage and 2 levels of concentrate (30 and 60% dry matter basis), with or without yeast supplement. At the end of each period, CH₄ emissions were measured simultaneously using the SF₆ and respiration chamber techniques when cows were housed in chambers. The SF₆ technique was also used when cows were housed in digestibility units (barn location) before and after respiratory chamber measurements (chamber location). The simultaneous measurements in chamber location revealed that CH₄ emission estimates by the SF₆ technique were similar to those by the respiration chamber technique in the first 3 periods, although the SF₆ estimates were significantly higher in period 4. The regression of all data from the 4 periods demonstrated a linear relationship between the SF₆ and respiration chamber measurements for total CH₄ emissions (g/d, R² = 0.69) and for CH₄ emissions per unit of milk yield (g/kg, R² = 0.88), and a quadratic relationship for CH₄ emissions per unit of dry matter intake (g/kg, R² = 0.64). The CH₄ emissions from the rectum were calculated as the difference between CH₄ estimates from the SF₆ technique when cows were housed in respiratory chambers and barn locations, which was 3% of the total CH₄ emissions from the mouth, nostrils, and rectum. The SF₆ estimates in the chamber location accounted for all sources of emissions, whereas those in the barn location, like that in grazing conditions, did not include CH₄ emission from the rectum. Therefore, the SF₆ measurements for grazing cattle should be adjusted for CH₄ emissions from the rectum (3% of total). We conclude that the SF₆ technique is reasonably accurate for estimating CH₄ emissions.

Technical options for the mitigation of direct methane and nitrous oxide emissions from livestock: a review

“…In ruminants, the vast majority of enteric CH 4 production occurs in the reticulo-rumen. Rectal emissions account for a marginal share of emissions (Murray et al, 1976;Muñ oz et al, 2012). A number of approaches, evaluated for mitigation of enteric CH 4 , are presented in Table 1.…”

The influence of grass silage-to-maize silage ratio and concentrate composition on methane emissions, performance and milk composition of dairy cows

“…The use of a Latin square design in the present study reduces this effect of permeation tube release rate as all animals received all diets. Boadi et al (2002) and Muñoz et al (2012) reported that using the SF 6 technique resulted in a larger variation around the mean compared with chamber measurements, although measurements were not conducted simultaneously. However, it must be remembered that, despite its limitations, the SF 6 technique is still the only methodology that allows individual animal measurements under normal production systems (Lassey and Ulyatt, 2000).…”

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

“…Pinares-Patiño et al 2008;Grainger et al 2010b;Muñoz et al 2012) or that the variance in methane yield measured by the original SF 6 technique was generally greater than the variance of methane yield measured by the chamber technique (Vlaming et al 2008;Hammond et al 2009Hammond et al , 2015.…”