Methane emissions and feeding behaviour of feedlot cattle supplemented with nitrate or urea

Abstract

Nitrate may serve as a non-protein nitrogen (NPN) source in ruminant diets while also reducing enteric methane emissions. A study was undertaken to quantify methane emissions of cattle when nitrate replaced urea in a high concentrate diet. Twenty Angus steers were allocated to two treatment groups and acclimated to one of two iso-energetic and iso-nitrogenous finisher rations (containing NPN as urea or as calcium nitrate), with all individual feeding events recorded. A single methane measurement device (C-lock Inc., Rapid City, SD, USA) was exchanged weekly between treatments (2 × 1-week periods per treatment) to provide estimations of daily methane production (DMP; g CH4/day). A 17% reduction in estimated DMP (P = 0.071) resulted from nitrate feeding, attributed to both a tendency for reduced dry matter intake (DMI; P = 0.088) and H2 capture by the consumed nitrate. NO3-fed cattle consumed a larger number of meals (14.69 vs 7.39 meals/day; P < 0.05) of smaller size (0.770 vs 1.820 kg/meal) each day, so the average interval between a feeding event and methane measurement was less in NO3-fed cattle (3.44 vs 5.15 h; P < 0.05). This difference could potentially have skewed the estimated DMP and contributed to the tendency (P = 0.06) for NO3-fed cattle to have a higher methane yield (g CH4/kg DMI) than urea-fed cattle. This study found short-term methane emission measurements made over 2 weeks (per treatment group) were adequate to show dietary nitrate tended to reduce emission and change the feeding pattern of feedlot cattle. Changes in feeding frequency may have confounded the ability of short-term methane measurements to provide data suitable for accurately estimating methane per unit feed intake.

Estimating daily methane production in individual cattle with irregular feed intake patterns from short-term methane emission measurements

“…Ramin and Huhtanen, 2013) they match observed data (MY 13.6 g/kg DMI) for similar concentrate diets (Hegarty et al, 2007) and with these same 24 animals measured in respiration chambers on the same diet (MY 15.5 g/kg DMI; Herd et al, unpublished data) 2 months later. The accuracy of using GEM has been shown (Velazco et al, 2014) through comparison with respiration chambers, so there is no reason to doubt the accuracy of the GEM as the CO 2 recoveries were high (95.9% and 97.9% of the gravimetrically determined quantities of CO 2 released into the shroud were recovered by the two GEM units used in the experiment). All model methane estimates and the average of spot estimates were lower than those predicted for feedlot cattle using Moe and Tyrell (1979).…”

“…Jonker et al, 2014). Velazco et al (2014) supplemented cattle with nitrate and reported unexpected DMP results using the GreenFeed emission monitoring (GEM) system that coincided with differences in time interval between feeding and GEM measurement, which may have skewed the estimates of DMP. This finding stimulated a more intensive examination of the relationship between DMP and feeding history of the animal.…”

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

“…They reported that nitrate-fed steers consumed more meals per day, resulting in a shorter time interval between consuming a meal and having methane measured by the GreenFeed system. 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).…”

“…There have been no Australian studies on dairy cows using the GreenFeed system. However, Velazco et al (2014) compared the methane emissions from Angus steers fed diets supplemented with either nitrate or urea. They reported that nitrate-fed steers consumed more meals per day, resulting in a shorter time interval between consuming a meal and having methane measured by the GreenFeed system.…”

Global beef cattle methane emissions: yield prediction by cluster and meta-analyses

“…MitiGate currently contains data from 412 sheep, beef and dairy cattle publications. The eight largest published beef MY datasets with all data needed for metaanalyses are from Herd et al (2014), Richmond et al (2015), Rooke et al (2014), McGinn et al (2009), Eugène et al (2011), Fitzsimons et al (2013), Boadi et al (2004) and Velazco et al (2014). Most of these datasets were missing from the MitiGate database at the time of our study, but were included in the metaanalysis presented in the current paper.…”