FEED SCIENCE AND TECHNOLOGY VOLUME 180 ISSUES 1-4 115-120 (2013) K. R. Lassey Abstract: Implementations of the sulphur hexafluoride (SF6) tracer technique to determine methane (CH4) emission rates from individual ruminant animals involve measuring levels of both CH4 and SF6 in background air. In well-ventilated settings, including grazing, background sampling is straightforward and the algebraic correction for background levels is then usually minor. In a recent paper in this journal (Vol. 170, p. 265–276), Williams et al. drew attention to the much more careful consideration that is needed for background sampling in experiments that use the SF6 tracer technique with housed animals when both CH4 and SF6 levels can build up unevenly within the housing. This note builds on that study to show specifically and rigorously: (a) what is meant by background air, and that background corrections to CH4 emission estimates are unaffected by the recycling of CH4 and SF6 through inhalation of self-exhaled gases; (b) that in studies of the role of various treatments on CH4 emission rates, the siting of background samplers can crucially impact on findings; and, in particular, (c) that reports of a possible dependence of estimated CH4 emission rates upon the rate of SF6 release in the rumen are called into question due to the sensitivity of those findings to the siting of background samplers. DATE Jan 16, 2013
J. DAIRY SCI. 95 :3181–3189 (2012) VARIATION AMONG INDIVIDUAL DAIRY COWS IN METHANE MEASUREMENTS MADE ON FARM DURING MILKING P. C. Garnsworthy ,1 J. Craigon , J. H. Hernandez-Medrano , and N. Saunders ABSTRACT The objective of this study was to quantify on-farm variation between and within cows in methane emissions measured during milking, and to determine which factors are related to this variation. Methane emission rate during milking (MERm) was recorded at milking using methane analyzers installed in automatic (robotic) milking stations for 215 cows over a period of 5 mo. Between-cow variation in MERm (mean 2.07, SD 0.629 g/min), was greater than within-cow variation and was related to variation in body weight, milk yield, parity, and week of lactation. Estimation of daily methane emissions from MERm data, using an equation derived from comparisons with respiration chamber data, produced estimates that ranged from 278 to 456 g of CH4/d and were commensurate with values predicted from metabolizable energy requirements for observed body weight and milk yield. It is concluded that methane emissions vary considerably between dairy cows housed under commercial conditions. This variation needs to be taken into account when performing inventories or testing mitigation strategies, but it might offer opportunities for genetic selection. DATE Oct 6, 2012 LOCATION J. Dairy Sci. 95: 3181-3189 CONTACT Phil Garnsworthy EMAIL Phil.Garnsworthy@nottingham.ac.uk WEBSITE dx.doi.org/ 10.3168/jds.2011-4606
JOURNAL OF DAIRY SCIENCE 95: 3166-3180 (2012) P. C. GARNSWORTHY ET AL Abstract The objective of this study was to investigate whether measurement of methane emissions by individual dairy cows during milking could provide a useful technique for monitoring on-farm methane emissions. To quantify methane emissions from individual cows on farm, we developed a novel technique based on sampling air released by eructation during milking. Eructation frequency and methane released per eructation were used to estimate methane emission rate. For 82 cows, methanee mission rate during milking increased with daily milk yield (r = 0.71), but varied between individuals with the same milk yield and fed the same diet. For 12 cows, methane emission rate recorded during milking on farm showed a linear relationship (R2 = 0.79) with daily methane output by the same cows when housed subsequently in respiration chambers. For 42 cows, the methane emission rate during milking was greater on a feeding regimen designed to produce high methane emissions, and the increase compared with a control regimen was similar to that observed for cows in respiration chambers. It was concluded that, with further validation, on-farm monitoring of methane emission rate during milking could provide a low-cost reliable method to estimate daily methane output by individual dairy cows, which could be used to study variation in methane, to identify cows with low emissions, and to test outcomes of mitigation strategies. DATE Oct 6, 2012 LOCATION J. Dairy Sci. 95 :3166 CONTACT Phil Garnsworthy EMAIL Phil.Garnsworthy@nottingham.ac.uk WEBSITE dx.doi.org/ 10.3168/jds.2011-4605
SIMPLE SUMMARY: A spring calving herd (~350 beef cows) over two production cycles was used to compare the whole-farm GHG emissions among calf-fed vs. yearling-fed production systems with and without growth implants. Farm GHG emissions initially included enteric CH4, manure CH4 and N2O, cropping N2O, and energy use CO2. The carbon footprint ranged from 19.9–22.5 kg CO2e per kg carcass weight. Including soil organic carbon loss from annual cropping and carbon sequestration from perennial pastures and haylands further reduced the carbon footprint by 11–16%. The carbon footprint of beef was reduced by growth promotants (4.9–5.1%) and by calf-fed beef production (6.3–7.5%). DATE Oct 4, 2012 LOCATION Animals 2012, 2 CONTACT John Basarab EMAIL john.basarab@gov.ab.ca WEBSITE dx.doi.org/ 10.3168/jds.2011-4606